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.

A004192 Numbers obtained by reversing digits of factorial numbers.

Original entry on oeis.org

1, 1, 2, 6, 21, 27, 42, 405, 2304, 88263, 88263, 861993, 6100974, 80207226, 219287178, 8634767031, 88898722902, 690824786553, 8275073732046, 238804001546121, 466718002092342, 4490717124909015, 867067777270004211, 4667948883761025852, 48958903334001211551
Offset: 0

Views

Author

N. J. A. Sloane

Keywords

Crossrefs

A sorted version of A004153.

Programs

  • Mathematica
    IntegerReverse[Range[0,30]!]//Sort (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 14 2021 *)

A062018 a(n) = n^n written backwards.

Original entry on oeis.org

1, 4, 72, 652, 5213, 65664, 345328, 61277761, 984024783, 1, 116076113582, 6528440016198, 352295601578203, 61085552860021111, 573958083098398734, 61615590737044764481, 771467633688162042728, 42457573569257080464393
Offset: 1

Views

Author

Amarnath Murthy, Jun 01 2001

Keywords

Examples

			a(5) = 5213, as 5^5 = 3125.

Links

Crossrefs

Cf. A004086, A004093, A004156, A034906, A004094, A004167, A002108, A002118, A002138, A002140, A002232, A002239, A002241, A002942, A004165, A004087, A004091, A004096, A004098, A004150, A004153.

Programs

  • Maple
    with(numtheory):for n from 1 to 50 do a := convert(n^n,base,10):b := add(10^(nops(a)- i)*a[i],i=1..nops(a)):printf(`%d,`,b); od:
  • Mathematica
    Table[IntegerReverse[n^n],{n,20}] (* Harvey P. Dale, Jul 31 2022 *)
  • PARI
    a(n) = { fromdigits(Vecrev(digits( n^n )))} \\ Harry J. Smith, Jul 29 2009

Formula

a(n) = A004086(n^n).

Extensions

More terms from Jason Earls and Vladeta Jovovic, Jun 01 2001

A103160 a(n) = GCD(reverse(n!), reverse((n+1)!)).

Original entry on oeis.org

1, 2, 6, 21, 3, 27, 9, 9, 88263, 9, 99, 594, 198, 99, 99, 99, 99, 99, 99, 9009, 99, 99, 198, 99, 99, 297, 1089, 99, 198, 198, 594, 198, 396, 693, 99, 99, 99, 297, 594, 99, 99, 99, 198, 99, 99, 99, 99, 99, 99, 99, 99, 396, 2772, 99, 99, 99, 396, 693, 693, 99, 99, 99, 99
Offset: 1

Views

Author

Labos Elemer, Jan 25 2005

Keywords

Comments

Through the first 200 terms, the largest term has 6 digits with the exception of a(99) which has 134 digits. - Harvey P. Dale, Dec 24 2018

Examples

			Outstandingly high values arise at n = 10^k - 1 because
A004153(n) = A004153(n+1), a(n) = rev(n!), n! written backwards.
See n = 9, 99, 999, etc.

Crossrefs

Cf. A000142, A004153.

Programs

  • Mathematica
    rd[x_] :=FromDigits[Reverse[IntegerDigits[x]]] Table[GCD[rd[w! ], rd[(w+1)! ]], {w, 1, 100}]
GCD@@#&/@Partition[IntegerReverse[Range[100]!],2,1] (* Harvey P. Dale, Dec 24 2018 *)
  • Python
    from math import factorial, gcd
def a(n):
    f = factorial(n)
    return gcd(int(str(f)[::-1]), int(str(f*(n+1))[::-1]))
print([a(n) for n in range(1, 64)]) # Michael S. Branicky, Dec 12 2021

Formula

a(n) = GCD(A004153((n+1)!), A004153(n!)).
Showing 1-3 of 3 results.

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

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