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 A045969 #14 Sep 19 2023 01:44:21
%S A045969 6,15,35,225,77,525,143,3375,1225,1155,221,7875,323,2145,2695,50625,
%T A045969 437,18375,667,17325,5005,3315,899,118125,5929,4845,42875,32175,1147,
%U A045969 40425,1517,759375,7735,6555,11011,275625,1763,10005,11305,259875,2021,75075
%N A045969 a(1)=6; if n = Product p_i^e_i, n>1, then a(n) = Product p_{i+1}^e_i * Product p_{i+2}^e_i.
%D A045969 From a puzzle proposed by _Marc LeBrun_.
%F A045969 Sum_{n>=1} 1/a(n) = -5/6 + Product_{k>=2} (1+1/(prime(k)*prime(k+1)-1)) = 0.31383788... . - _Amiram Eldar_, Sep 19 2023
%t A045969 f[p_, e_] := (NextPrime[p] * NextPrime[p, 2])^e; a[1] = 6; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Sep 19 2023 *)
%Y A045969 Cf. A045965, A045966, A045967, A045968, A045970, A045971, A045972, A045973.
%K A045969 easy,nonn
%O A045969 1,1
%A A045969 _N. J. A. Sloane_
%E A045969 More terms from _David W. Wilson_