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

Author

Jon Perry, Mar 22 2004

Keywords

• nonn

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

Crossrefs

Cf. A000005, A092403, A175143, A346562.

Programs

Mathematica

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

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

Formula

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

Extensions

Extended by Ray Chandler, Mar 05 2010