cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A115651 Powerful(1) numbers (A001694) which are the sum of distinct double factorials (A006882).

Original entry on oeis.org

1, 4, 8, 9, 16, 25, 27, 49, 64, 72, 108, 121, 125, 128, 169, 392, 400, 432, 441, 500, 512, 961, 968, 972, 1125, 1331, 1352, 1444, 3844, 3888, 3969, 4225, 4232, 4356, 4900, 4913, 5184, 5292, 5324, 10404, 10800, 10952, 11449, 11881, 14283, 14400
Offset: 1

Views

Author

Giovanni Resta, Jan 28 2006

Keywords

Comments

Double factorials 0!! and 1!! are not considered distinct. Note that double factorial (n!!) is different from (n!)!.

Examples

			392 = 2^3*7^2 = 8!! + 4!!.

Links

Crossrefs

Cf. A001694, A006882, A115652, A115653, A115654.

A115652 Brilliant numbers (A078972) which are the sum of distinct double factorials (A006882).

Original entry on oeis.org

4, 6, 9, 10, 14, 15, 21, 25, 49, 121, 169, 403, 407, 437, 451, 493, 517, 551, 949, 961, 1003, 1007, 1067, 1073, 1079, 1121, 1333, 1343, 1349, 1357, 1387, 1403, 1457, 1501, 3869, 3901, 3953, 4331, 4891, 5183, 5293, 10403, 10807, 11413, 11449
Offset: 1

Views

Author

Giovanni Resta, Jan 28 2006

Keywords

Comments

Double factorials 0!! and 1!! are not considered distinct. Note that double factorial (n!!) is different from (n!)!.

Examples

			949 = 13*73 = 9!! + 3!! + 1!!.

Crossrefs

Cf. A006882, A078972, A115651, A115653, A115654.

A115654 Semiprimes (A001358) which are the sum of distinct double factorials (A006882).

Original entry on oeis.org

4, 6, 9, 10, 14, 15, 21, 25, 26, 49, 51, 57, 58, 62, 65, 69, 74, 77, 106, 111, 115, 118, 119, 121, 122, 123, 129, 133, 134, 155, 158, 159, 161, 166, 169, 177, 178, 386, 393, 394, 395, 398, 403, 407, 411, 413, 437, 445, 446, 447, 451, 453, 458, 489, 493, 497
Offset: 1

Views

Author

Giovanni Resta, Jan 28 2006

Keywords

Comments

Double factorials 0!! and 1!! are not considered distinct. Note that double factorial (n!!) is different from (n!)!.

Examples

			384 = 2*19 = 8!!+2!!.

Crossrefs

Cf. A006882, A001358, A115651, A115652, A115653.

Programs

  • Mathematica
    Union[Select[Total/@Subsets[Range[10]!!,10],PrimeOmega[#]==2&]] (* Harvey P. Dale, Aug 24 2012 *)
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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