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 1-2 of 2 results.

A159554 a(n) = A159553(n)/n.

Original entry on oeis.org

2, 3, 4, 7, 8, 24, 20, 67, 96, 256, 188, 1060, 632, 3228, 5244, 11427, 7712, 51888, 27596, 184912, 232888, 606628, 364724, 2807936, 2405184, 8671944, 10368080, 36873652, 18512792, 167268640, 69273668, 496472227, 551130064, 1856103040
Offset: 1

Views

Author

Leroy Quet, Apr 14 2009

Keywords

Comments

a(n) = A159069(n) + 1.

Crossrefs

Cf. A159069, A159553.

Extensions

Extended by Ray Chandler, Jun 18 2009

A159555 Numbers m where m^2 divides A159553(m), where A159553(m) = Sum_{k=0..m} binomial(m,k) * gcd(m,k).

Original entry on oeis.org

1, 6, 22, 72, 114, 148, 164, 260, 261, 780, 1078, 1184, 1266, 2952, 4674, 21868
Offset: 1

Views

Author

Leroy Quet, Apr 15 2009

Keywords

Comments

For the purpose of this sequence, gcd(m,0) = m.
No other term up to 15000. - Michel Marcus, Sep 06 2019

Crossrefs

Cf. A159458, A159553, A159554.

Programs

  • Maple
    A159068 := proc(n) option remember; add(binomial(n, k)*gcd(k, n), k=1..n) ; end: A159553 := proc(n) option remember ; A159068(n)+n; end: isA159555 := proc(n) if A159553(n) mod ( n^2) = 0 then true; else false; fi; end: for n from 1 do if isA159555(n) then printf("%d,\n",n) ; fi; od: # R. J. Mathar, Apr 29 2009
  • PARI
    f(n) = sum(k=0, n, binomial(n,k) * gcd(n,k)); \\ A159553
isok(n) = !(f(n) % n^2); \\ Michel Marcus, Sep 05 2019

Extensions

Extended by R. J. Mathar, Apr 29 2009
a(14)-a(15) from Ray Chandler, Jun 18 2009
a(16) from Jinyuan Wang, Jul 25 2022
Showing 1-2 of 2 results.

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