A173669 Numbers k which divide number of groups of order <= k (A063756).

1, 2, 3, 12, 26, 31, 84, 119, 248, 1107, 1543, 1683

Offset

1,2

Comments

No other terms up to 2047. - Eric M. Schmidt, Feb 10 2013

Links

Table of n, a(n) for n=1..12.

Formula

{k: k | A063756(k)} == {k: k | SUM[i=1..k] A000001(i)}.

Example

a(1) = 1 because 1 divides (the number of groups of order <= 1) = (number of groups of order 1) = 1.
a(4) = 12 because 12 divides (the number of groups of order <= 12) = 24.
a(5) = 26 because 26 divides (the number of groups of order <= 26) = 78 = 3 * 26.
a(6) = 31 because 31 divides (the number of groups of order <= 31) = 93 = 3 * 31.

Prog

(GAP) A173669 := function(max) local n, res, i; n := 0; res := []; for i in [1..max] do n := n + NrSmallGroups(i); if n mod i = 0 then Add(res, i); fi; od; return res; end; # Eric M. Schmidt, Feb 10 2013

Crossrefs

Cf. A000001, A063756.

Sequence in context: A148070 A187994 A016021 * A136703 A349016 A249490

Adjacent sequences: A173666 A173667 A173668 * A173670 A173671 A173672

Keyword

nonn,more

Author

Jonathan Vos Post, Nov 24 2010

Extensions

More terms from Eric M. Schmidt, Feb 10 2013

Status

approved