This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A275630 #18 Jan 31 2021 08:14:27 %S A275630 3,2,6,6,30,42,6,30,66,210,30,114,210,462,138,78,870,930,1122,210,222, %T A275630 390,1722,330,42,510,1326,318,330,798,42,4290,2346,4830,1110,570,6162, %U A275630 246,3486,7482,2670,2730,570,582,462,330,11130,1554,12882,13110,2262,3570,330,210,258,8646,2010 %N A275630 a(n) = product of distinct primes dividing prime(n)^2 - 1. %H A275630 Amiram Eldar, <a href="/A275630/b275630.txt">Table of n, a(n) for n = 1..10000</a> %F A275630 a(n) = A007947(A084920(n)). - _Michel Marcus_, Jan 30 2021 %F A275630 a(n) = A077063(n)*A077066(n)/2, for n > 1. - _Amiram Eldar_, Jan 30 2021 %t A275630 a[n_] := Times @@ FactorInteger[Prime[n]^2 - 1][[;; , 1]]; Array[a, 60] (* _Amiram Eldar_, Jan 30 2021 *) %o A275630 (PARI) a(n) = factorback(factorint(prime(n)^2-1)[, 1]); \\ _Michel Marcus_, Jan 30 2021 %Y A275630 Subsequence of A007947. %Y A275630 Cf. A077063, A077066, A084920. %K A275630 nonn %O A275630 1,1 %A A275630 _N. J. A. Sloane_, Aug 07 2016