A341664 a(n) is the number of divisors of prime(n)^5 - 1.
2, 6, 12, 8, 12, 12, 10, 24, 8, 12, 48, 72, 24, 16, 32, 48, 64, 72, 32, 96, 24, 16, 8, 64, 96, 96, 32, 16, 96, 80, 24, 48, 64, 32, 48, 32, 96, 160, 32, 24, 16, 108, 96, 28, 72, 48, 96, 128, 8, 48, 32, 16, 120, 60, 36, 8, 36, 96, 24, 192, 64, 24, 96, 48, 64, 48
Offset: 1
Keywords
Examples
p = factorization n prime(n) p^5 - 1 of p^5 - 1 a(n) - -------- ------- ------------------ ---- 1 2 31 31 2 2 3 242 2 * 11^2 6 3 5 3124 2^2 * 11 * 71 12 4 7 16806 2 * 3 * 2801 8 5 11 161050 2 * 5^2 * 3221 12 6 13 371292 2^2 * 3 * 30941 12 7 17 1419856 2^4 * 88741 10 8 19 2476098 2 * 3^2 * 151 * 911 24 9 23 6436342 2 * 11 * 292561 8 ...
Programs
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Mathematica
a[n_] := DivisorSigma[0, Prime[n]^5 - 1]; Array[a, 50] (* Amiram Eldar, Feb 26 2021 *)
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PARI
a(n) = numdiv(prime(n)^5-1); \\ Michel Marcus, Feb 26 2021
Comments