Ulam Number Checker is a free online tool used to check if the given number is an Ulam number.
What is an Ulam number?
Ulam numbers are devised by Stainislaw Ulam in 1964. It is an integer sequence where Un is the smallest integer, which is the sum of two distinct earlier items in exactly one way and that is larger than the earlier items. The first two of the Ulam sequence are U1 = 1 and U2 = 2.
For example
3 = 1 + 2, meet the condition, it is an Ulam number.
4 = 1 + 3, meet the condition, it is an Ulam number.
5 = 1 + 4 or 2 + 3. So, 5 is not an Ulam number.
6 = 2 + 4, it is an Ulam number.
7 = 1 + 6 or 3 + 4. Not an Ulam number.
8 = 2 + 6. An Ulam number.
9 = 1 + 8 or 3 + 6. Not an Ulam number.
10 = 2 + 8 or 4 + 6. Not an Ulam number.
First 100 numbers in Ulam sequence
- 1
- 2
- 3
- 4
- 6
- 8
- 11
- 13
- 16
- 18
- 26
- 28
- 36
- 38
- 47
- 48
- 53
- 57
- 62
- 69
- 72
- 77
- 82
- 87
- 97
- 99
- 102
- 106
- 114
- 126
- 131
- 138
- 145
- 148
- 155
- 175
- 177
- 180
- 182
- 189
- 197
- 206
- 209
- 219
- 221
- 236
- 238
- 241
- 243
- 253
- 258
- 260
- 273
- 282
- 309
- 316
- 319
- 324
- 339
- 341
- 356
- 358
- 363
- 370
- 382
- 390
- 400
- 402
- 409
- 412
- 414
- 429
- 431
- 434
- 441
- 451
- 456
- 483
- 485
- 497
- 502
- 522
- 524
- 544
- 546
- 566
- 568
- 585
- 602
- 605
- 607
- 612
- 624
- 627
- 646
- 668
- 673
- 685
- 688
- 690
How to use the Ulam number checker
The procedure to use the Ulam number checker is as follows:
- Enter the positive integer.
- Click Calculate button to verify whether the input integer is an Ulam number.
- Click the Reset button to start a new verification.
Solved examples using the Ulam number checker
Example 1: Is 905 an Ulam number?
Enter 905 into the input box and click Calculate button, as shown in the figure, 905 is an Ulam number.
Example 2: Is 2030 an Ulam number?
Enter 2030 into the input box and click Calculate button, as shown in the figure, 2030 is not an Ulam number.
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