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 A276939 #13 Jun 24 2023 19:17:11 %S A276939 3,8,36,240,2520,32340,540540,10210200,232792560,6692786100, %T A276939 207030183360,7621298624940,311671001662020,13387011595197240, %U A276939 627972543920161440,33204048259778536140,1955349508631402683800,119211141709561183622340,7975609932439674026862360,565799151677779228023294480,41287621429375723111588738860 %N A276939 Row 2 of A276945: a(n) = A002110(n) + A002110(n+1). %C A276939 a(n) = number whose primorial base representation (A049345) begins with digits "11", followed by n zeros: 11, 110, 1100, 11000, 110000, ... %H A276939 Michael De Vlieger, <a href="/A276939/b276939.txt">Table of n, a(n) for n = 0..349</a> %H A276939 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a> %F A276939 a(n) = A002110(n) + A002110(n+1). %t A276939 Total /@ Partition[FoldList[Times, 1, Prime@ Range[20]], 2, 1] (* _Michael De Vlieger_, Jun 24 2023 *) %o A276939 (Scheme) (define (A276939 n) (+ (A002110 n) (A002110 (+ 1 n)))) %o A276939 (PARI) a(n) = factorback(primes(n)) + factorback(primes(n+1)); \\ _Michel Marcus_, Nov 23 2022 %Y A276939 Row 2 of A276945 (column 2 of A276943). %Y A276939 Cf. A002110, A049345. %K A276939 nonn,base %O A276939 0,1 %A A276939 _Antti Karttunen_, Sep 24 2016