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.

A128372 a(n) = least k such that the remainder when 32^k is divided by k is n.

Original entry on oeis.org

31, 3, 29, 6, 201, 13, 25, 9, 23, 11, 183, 22, 19, 159, 17, 20, 45, 49, 169, 502, 209, 42, 35, 50, 91919, 27, 3265, 36, 1159, 98, 75197, 33, 95, 66, 2817, 38, 1385, 58, 25187, 82, 32727, 982, 55, 117, 7031, 91, 2517, 52, 46528545441593, 57, 503981, 92, 135, 194
Offset: 1

Views

Author

Alexander Adamchuk, Feb 27 2007

Keywords

Comments

Values a(50), ..., a(149) are relatively small again (starting 57, 503981, 92, 135, 194, 576353, 87, 125, 1902, 6019, 323, 43335727, 69, ...). - Hagen von Eitzen, Jun 04 2009

Crossrefs

Programs

  • Mathematica
    t = Table[0, {10000} ]; k = 1; While[ k < 4000000000, a = PowerMod[32, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t (* Robert G. Wilson v, Aug 06 2009 *)

Extensions

Incorrect comment removed by Hagen von Eitzen, Jul 19 2009
a(49) found by Hagen von Eitzen, Jul 20 2009

A128371 a(n) = least k such that the remainder when 31^k is divided by k is n.

Original entry on oeis.org

2, 29, 7, 29787, 13, 113413, 51, 23, 11, 3309, 38, 19, 21, 17, 22, 115, 118, 37237, 261, 60212617, 94, 29769, 134, 51205605391, 26, 35, 209, 549, 466, 1558391, 37, 5033228393, 58, 39, 926, 565, 57, 1561, 922, 119, 46, 2512157, 111, 949, 76, 85
Offset: 1

Views

Author

Alexander Adamchuk, Feb 27 2007

Keywords

Crossrefs

Programs

  • Mathematica
    t = Table[0, {10000} ]; k = 1; While[ k < 4750000000, a = PowerMod[31, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t (* Robert G. Wilson v, Aug 06 2009 *)

Extensions

More terms from Ryan Propper, Mar 24 2007
a(494) = 14353729267 = 64609 * 222163. a(498) = 9547024387, a(540) = 29711794103. - Daniel Morel, Jun 17 2010. a(618) = 15150617101, a(750) = 13728669221. - Daniel Morel, Jun 28 2010

A128370 a(n) = least k such that the remainder of 30^k divided by k is n.

Original entry on oeis.org

29, 7, 26997, 13, 8471, 33, 23, 11, 721, 55, 19, 39, 17, 886, 21, 26, 803, 98, 13289, 22, 51, 878, 1141, 146, 35, 38, 111, 218, 515267673651961, 31, 3212679202339, 56, 267, 866, 4367, 42, 10129, 862, 57, 86, 42691, 13479, 949, 214, 95, 77, 7633, 52, 1469, 170, 429, 68, 2791229, 94, 215, 422, 3849, 842, 9773, 140
Offset: 1

Views

Author

Alexander Adamchuk, Feb 27 2007

Keywords

Crossrefs

Programs

  • Mathematica
    t = Table[0, {10000} ]; k = 1; While[ k < 5100000000, a = PowerMod[30, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t (* Robert G. Wilson v, Aug 06 2009 *)

Extensions

Terms a(29) onward from Max Alekseyev, Mar 22 2012

A129368 a(n) = Sum_{k=floor((n+1)/2)..n} binomial(2*k,k).

Original entry on oeis.org

1, 2, 8, 26, 96, 342, 1266, 4678, 17548, 66098, 250854, 956034, 3660190, 14059866, 54176466, 209290554, 810370944, 3143964294, 12219099594, 47564314774, 185410843594, 723668533278, 2827767496998, 11061197519166
Offset: 0

Views

Author

Paul Barry, Apr 11 2007

Keywords

Comments

Partial sums of A129369.

Crossrefs

Cf. A129369.

Programs

  • Magma
    [(&+[Binomial(2*(n-k),n-k): k in [0..Floor(n/2)]]): n in [0..60]]; // G. C. Greubel, Jan 31 2024
    
  • Mathematica
    Table[Sum[Binomial[2k,k],{k,Floor[(n+1)/2],n}],{n,0,30}] (* Harvey P. Dale, Aug 13 2012 *)
  • SageMath
    [sum(binomial(2*(n-k),n-k) for k in range(1+(n//2))) for n in range(61)] # G. C. Greubel, Jan 31 2024

Formula

G.f.: (1/(1-x))*( 1/sqrt(1-4*x) - x/sqrt(1-4*x^2) ).
a(n) = Sum_{k=0..floor(n/2)} C(2*(n-k), n-k).
Showing 1-4 of 4 results.