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.

A115653 Prime numbers which are the sum of distinct double factorials (A006882).

Original entry on oeis.org

2, 3, 5, 11, 13, 17, 19, 23, 29, 53, 59, 61, 67, 71, 73, 107, 109, 113, 131, 157, 163, 167, 173, 179, 181, 389, 397, 401, 409, 433, 443, 449, 457, 461, 491, 499, 503, 509, 541, 547, 557, 563, 947, 953, 971, 997, 1009, 1013, 1019, 1021, 1051, 1061, 1063
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

			947 is prime and 947 = 9!! + 2!!.

Crossrefs

Cf. A006882, A115651, A115652, 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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