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 1-4 of 4 results.

A097653 Numbers n such that n=d_1!!+d_2!!+...+d_k!! where d_1 d_2 ... d_k is the decimal expansion of n.

Original entry on oeis.org

1, 2, 3, 107
Offset: 1

Views

Author

Farideh Firoozbakht, Sep 10 2004

Keywords

Examples

			107 is in the sequence because 1!!+0!!+7!!=1+1+7*5*3*1=107.

Crossrefs

Cf. A097654, A097655, A097643.

Programs

  • Mathematica
    Do[h=IntegerDigits[n];l=Length[h];If[n==Sum[h[[k]]!!, {k, l}], Print[n]], {n, 4*9!!}]

A097655 Numbers n such that n = d_1!!*d_2!!*...*d_k!! where d_1 d_2 ... d_k is the decimal expansion of n.

Original entry on oeis.org

1, 2, 3, 15, 18432, 75600, 276531978240000, 4810168001497883738112000, 215788176336727572480000000, 2178419737991700039289327133392896000000000000
Offset: 1

Views

Author

Farideh Firoozbakht, Sep 10 2004

Keywords

Comments

All terms are of the form 2^i*3^j*5^k*7^l.

Examples

			18432 is in the sequence because 18432 = 1!!*8!!*4!!*3!!*2!!.

Crossrefs

Cf. A097653, A097654, A097643, A102279.

Programs

  • Mathematica
    Do[h=IntegerDigits[n];l=Length[h];If[n==Product[h[[k]]!!, {k, l}], Print[n]], {n, 2000000000}]

Extensions

More terms from Farideh Firoozbakht, Jan 08 2005

A097642 Numbers k such that k = (d_1! + d_2! + ... + d_k!) - (d_1 + d_2 + ... + d_k) where d_1 d_2 ... d_k is the decimal expansion of k.

Original entry on oeis.org

3, 115, 6576, 80855
Offset: 1

Views

Author

Farideh Firoozbakht, Aug 22 2004

Keywords

Examples

			80855 is in the sequence because 80855 = (8! + 0! + 8! + 5! + 5!) - (8 + 0 + 8 + 5 + 5).

Crossrefs

Cf. A097643.

Programs

  • Mathematica
    okQ[n_]:=Module[{idn=IntegerDigits[n]},n==Total[idn!]-Total[idn]]; Select[Range[81000],okQ] (* Harvey P. Dale, Aug 26 2011 *)

A097654 Numbers n such that n=|d_1!!-d_2!!+...+(-1)^(k-1)*d_k!!| where d_1 d_2 ... d_k is the decimal expansion of n.

Original entry on oeis.org

1, 2, 3, 380
Offset: 1

Views

Author

Farideh Firoozbakht, Sep 10 2004

Keywords

Examples

			380 is in the sequence because 380=|3!!-8!!+0!!|.

Crossrefs

Cf. A097653, A097655, A097643.

Programs

  • Mathematica
    Do[h=IntegerDigits[n];l=Length[h];If[n==Abs[Sum[(-1)^(k-1) *h[[k]]!!, {k, l}]], Print[n]], {n, 4*9!!}]
Showing 1-4 of 4 results.

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

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