A076136 -id:A076136 - cp's OEIS frontend

A332974 Solutions k of the equation s(k) = s(k-1) + s(k-2) where s(k) = usigma(k) - k is the sum of proper unitary divisors of k (A063919).

3, 21, 321, 1257, 3237, 146139, 268713, 584835, 26749089, 9988999095, 25997557299, 54449485353, 935628578283, 2105722150095, 3921293253003, 8234992646643

Offset: 1

Amiram Eldar, Mar 04 2020

a(17) > 10^13. - Giovanni Resta, May 09 2020

			21 is a term since s(21) = 11 and s(19) + s(20) = 1 + 10 = 11.

The unitary version of A291176.

Cf. A063919, A065557, A065900, A075565, A076136, A145469, A291126, A292033, A294995, A332973.

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); s[n_] := usigma[n] - n; Select[Range[3, 6*10^5], s[#] == s[# - 1] + s[# - 2] &]

a(12)-a(16) from Giovanni Resta, May 09 2020

A332976 Solutions k of the equation s(k) = s(k-1) + s(k-2) where s(k) = isigma(k) - k is the sum of proper infinitary divisors of k (A126168).

Original entry on oeis.org

3, 8, 10, 21, 3237, 7377, 146139, 584835, 9988999095, 25997557299

Offset: 1

Amiram Eldar, Mar 04 2020

			8 is a term since s(8) = 7 and s(6) + s(7) = 6 + 1 = 7.

The infinitary version of A291176.

Cf. A065557, A065900, A075565, A076136, A076251, A126168, A145469, A291126, A292033, A294995, A332975.

fun[p_, e_] := Module[{b = IntegerDigits[e, 2]}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ fun @@@ FactorInteger[n]; s[n_] := isigma[n] - n; Select[Range[3, 6*10^5], s[#] == s[# - 1] + s[# - 2] &]

cp's OEIS Frontend

A332974 Solutions k of the equation s(k) = s(k-1) + s(k-2) where s(k) = usigma(k) - k is the sum of proper unitary divisors of k (A063919).

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