A109727 Number of admirable numbers < 10^n.

0, 13, 65, 379, 2549, 19480, 159001, 1345929, 11676912, 103136395

Offset

1,2

Links

Table of n, a(n) for n=1..10.

Mathematica

fQ[n_] := Block[{d = Most[Divisors[n]], k = 1}, l = Length[d]; s = Plus @@ d; While[k < l && s - 2d[[k]] > n, k++ ]; If[k > l || s != n + 2d[[k]], False, True]]; c = 0; k = 1; Do[ While[k <= 10^n, If[ fQ[k], c++ ]; k++ ]; k++; Print[c], {n, 7}] (* Robert G. Wilson v *)

Crossrefs

Cf. A111592.

Sequence in context: A147067 A147075 A268777 * A041320 A058380 A129746

Adjacent sequences: A109724 A109725 A109726 * A109728 A109729 A109730

Keyword

nonn

Author

Jason Earls, Aug 10 2005

Extensions

a(7) from Robert G. Wilson v, Aug 13 2005

a(8)-a(10) from Donovan Johnson, Jan 25 2012

Status

approved