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 A086489 #10 Mar 06 2019 10:08:55 %S A086489 2,3,2,3,2,5,14,3,2,3,2,5,21,3,2,3,2,5,8,3,2,7,10,5,10,3,2,3,2,7,15,5, %T A086489 6,3,2,5,14,3,2,3,2,5,14,3,2,7,10,5,6,3,2,6,21,5,10,3,2,3,2,7,21,5,6, %U A086489 3,2,5,10,3,2,3,2,7,14,5,10,3,2,5,6,3,2,7,10,5,6,3,2,6,6,7,15,5,22,3,2,5,14 %N A086489 Smallest k such that k and k + n have the same prime signature. %H A086489 Alois P. Heinz, <a href="/A086489/b086489.txt">Table of n, a(n) for n = 1..20000</a> %e A086489 a(7) = 14 as 14 and 14+7 = 21 have the same prime signature p*q. %e A086489 a(13) = 21 as 21 is the smallest number such that 21 +13 = 34 and 21 both have the same prime signature p*q. %e A086489 a(19) = 8 as 8 +19 = 27 = 3^3,8 = 2^3 both have the prime signature p^3. %o A086489 (PARI) ps(n) = local(f); f = factor(n); vecsort(f[,2]); a(n) = local(P, m, v); P = vector(n, i, ps(i)); m = 1; while (1, for (i = 1, n, v = ps(m*n + i); if (v == P[i], return((m - 1)*n + i), P[i] = v)); m++); \\ _David Wasserman_, Mar 09 2005 %Y A086489 Cf. A085072, A085876. %K A086489 nonn %O A086489 1,1 %A A086489 _Amarnath Murthy_, Jul 28 2003 %E A086489 More terms from _David Wasserman_, Mar 09 2005