A092405 a(n) = tau(n) + tau(n+1), where tau(n) = A000005(n), the number of divisors of n.

3, 4, 5, 5, 6, 6, 6, 7, 7, 6, 8, 8, 6, 8, 9, 7, 8, 8, 8, 10, 8, 6, 10, 11, 7, 8, 10, 8, 10, 10, 8, 10, 8, 8, 13, 11, 6, 8, 12, 10, 10, 10, 8, 12, 10, 6, 12, 13, 9, 10, 10, 8, 10, 12, 12, 12, 8, 6, 14, 14, 6, 10, 13, 11, 12, 10, 8, 10, 12, 10, 14, 14, 6, 10, 12, 10, 12, 10, 12, 15, 9, 6, 14, 16

Offset

1,1

Comments

If a child is born to an n-year-old parent, this is the number of times the age of the parent will be a multiple of the age of the child. E.g., if n = 27, this will happen at the ages (28, 1), (29, 1),(30, 2), (30, 3), (32, 4), (35, 7), (42, 14), (36, 9), (54, 27), (56, 28). - Alexander Piperski, Sep 10 2018

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Formula

a(n) = A346562(n+1,n). - Omar E. Pol, Jul 23 2021

Mathematica

Total /@ Partition[Array[DivisorSigma[0, #] &, 85], 2, 1] (* Michael De Vlieger, Sep 18 2018 *)

Prog

(PARI) for(i=1, 60, print1(", "sigma(i, 0)+sigma(i+1, 0)))
(PARI) A092405(n) = (numdiv(n)+numdiv(1+n)); \\ Antti Karttunen, Oct 07 2017

Crossrefs

Cf. A000005, A092403, A175143, A346562.

Sequence in context: A266898 A370302 A098200 * A130234 A108852 A179413

Adjacent sequences: A092402 A092403 A092404 * A092406 A092407 A092408

Keyword

nonn

Author

Jon Perry, Mar 22 2004

Extensions

Extended by Ray Chandler, Mar 05 2010

Status

approved