A191150 Hypersigma(n): sum of the divisors of n plus the recursive sum of the divisors of the restricted divisors.

1, 3, 4, 10, 6, 19, 8, 28, 17, 27, 12, 64, 14, 35, 34, 72, 18, 82, 20, 88, 44, 51, 24, 188, 37, 59, 61, 112, 30, 165, 32, 176, 64, 75, 62, 290, 38, 83, 74, 252, 42, 209, 44, 160, 139, 99, 48, 512, 65, 166, 94, 184, 54, 306, 90, 316, 104, 123, 60, 588, 62, 131

Offset

1,2

Comments

First we add up all the divisors of n, and then we add in the divisors of each restricted divisor of n (not 1 or n itself) and continue the recursion until such a depth as that there only numbers with no restricted divisors (prime numbers).

Thus if n is prime then hypersigma(n) is the same as sigma(n).

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000 (first 1000 terms from Alonso del Arte)

Formula

a(n) = n + 1 <=> n is prime. - Bill McEachen, Aug 01 2023

Example

a(12) = 64 since: the sum of the divisors of 12 is 28; to 28 we add 3 and 4 (corresponding to the prime divisors 2 and 3) bringing us up to 35; for 4 and 6 we continue the recursion, with 4 bringing us up to 45 and 6 brings up to 64.

Maple

a:= proc(n) option remember; uses numtheory;
      sigma(n)+add(a(d), d=divisors(n) minus {1, n})
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, Aug 01 2023

Mathematica

hyperSigma[1] := 1; hyperSigma[n_] := hyperSigma[n] = Module[{d=Divisors[n]}, Total[d] + Total[hyperSigma /@ Rest[Most[d]]]]; Table[hyperSigma[n], {n, 100}] (* From T. D. Noe with a slight modification *)

Crossrefs

Cf. A000040, A000203, A008864.

Sequence in context: A247372 A143443 A139556 * A023896 A328711 A361655

Adjacent sequences: A191147 A191148 A191149 * A191151 A191152 A191153

Keyword

nonn,easy

Author

Alonso del Arte, May 26 2011

Extensions

Example corrected by Paolo P. Lava, Jul 13 2011

Status

approved