A074495 a(n) = the first prime > sigma(n).
2, 5, 5, 11, 7, 13, 11, 17, 17, 19, 13, 29, 17, 29, 29, 37, 19, 41, 23, 43, 37, 37, 29, 61, 37, 43, 41, 59, 31, 73, 37, 67, 53, 59, 53, 97, 41, 61, 59, 97, 43, 97, 47, 89, 79, 73, 53, 127, 59, 97, 73, 101, 59, 127, 73, 127, 83, 97, 61, 173, 67, 97, 107, 131, 89, 149, 71, 127, 97, 149, 73, 197, 79, 127, 127, 149, 97, 173, 83
Offset: 1
Examples
The least prime > sigma(6) = 12 is 13, so a(6) = 13. The least prime > sigma(7) = 8 is 11, so a(7) = 11.
Links
Programs
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Mathematica
p[n_] := Module[{r, i}, r = 2; i = 1; While[r <= n, i = i + 1; r = Prime[i]]; r]; Table[p[DivisorSigma[1, n]], {n, 1, 40}] -
PARI
A074495(n) = nextprime(1+sigma(n)); \\ Antti Karttunen, Nov 16 2017
Formula
Extensions
More terms from Antti Karttunen, Nov 16 2017