A140645 Digit sums of highly composite numbers.

1, 2, 4, 6, 3, 6, 9, 12, 6, 3, 9, 6, 9, 9, 12, 9, 15, 9, 9, 18, 9, 9, 9, 9, 18, 18, 9, 18, 18, 18, 18, 18, 18, 18, 36, 18, 27, 18, 18, 18, 18

Offset

1,2

Comments

Except for the first three terms, all others are multiples of 3.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Achim Flammenkamp, Table of 1200 Highly Composite Numbers.

Graeme McRae, Highly Composite Numbers.

Formula

a(n) = A007953(A002182(n)). - Amiram Eldar, Nov 13 2019

Example

2162160 is a highly composite number whose digit sum is 18.

Mathematica

HCN=NestList[Function[last, Module[{d = DivisorSigma[0, last]}, NestWhile[# + 1 &, last, DivisorSigma[0, #] <= d &]]], 1, 40]; DigitSum/@HCN (* James C. McMahon, Jul 12 2025 *)

Crossrefs

Cf. A002182, A002183, A007953, A117825, A127390.

Sequence in context: A396029 A161184 A349543 * A327724 A117532 A287662

Adjacent sequences: A140642 A140643 A140644 * A140646 A140647 A140648

Keyword

nonn,base

Author

Parthasarathy Nambi, Jul 08 2008

Status

approved