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 A336905 #10 Jul 17 2021 04:29:40
%S A336905 1,6,15,30,35,77,100,105,143,210,221,323,385,437,441,462,667,858,899,
%T A336905 1001,1147,1155,1326,1517,1763,1938,2021,2145,2310,2431,2491,2622,
%U A336905 2744,3025,3127,3315,3599,4002,4087,4199,4290,4757,4845,5005,5183,5394,5767,6006
%N A336905 Numbers n such that for any i > 0 there is some j > 0 such that the prime(i)-adic valuation of n, say x, equals the prime(j)-adic valuation of n and x = abs(i-j) (where prime(k) denotes the k-th prime number and the p-adic valuation of a number is the greatest m such that p^m divides that number).
%C A336905 This sequence has connections with A336880.
%C A336905 All products of two successive prime numbers (A006094) belong to this sequence.
%C A336905 The product of two terms that are coprime is also a term.
%e A336905 Regarding 14300:
%e A336905 - 14300 = 2^2 * 5^2 * 11 * 13 = prime(1)^2 * prime(3)^2 * prime(5) * prime(6),
%e A336905 - the 2-adic valuation is in correspondence with the 5-adic valuation,
%e A336905 - the 11-adic valuation is in correspondence with the 13-adic valuation,
%e A336905 - the p-adic valuation is in correspondence with itself for any prime number p that does not divide 14300,
%e A336905 - so 14300 is a term.
%o A336905 (PARI) is(n) = { my (f=factor(n), x=f[,2]~, pi=apply(primepi, f[,1]~), u, v); for (k=1, #x, if (((u=setsearch(pi, pi[k]-x[k])) && x[u]==x[k]) || ((v=setsearch(pi, pi[k]+x[k])) && x[v]==x[k]), "OK", return (0))); return (1) }
%Y A336905 Cf. A006094, A336880.
%K A336905 nonn
%O A336905 1,2
%A A336905 _Rémy Sigrist_, Aug 07 2020