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 A373607 #8 Jun 18 2024 18:01:47
%S A373607 0,0,1,1,2,2,0,0,1,1,2,2,0,0,1,1,2,2,0,0,1,1,2,2,0,0,1,1,2,2,1,1,2,2,
%T A373607 3,3,1,1,2,2,3,3,1,1,2,2,3,3,1,1,2,2,3,3,1,1,2,2,3,3,2,2,3,3,4,4,2,2,
%U A373607 3,3,4,4,2,2,3,3,4,4,2,2,3,3,4,4,2,2,3,3,4,4,3,3,4,4,5,5,3,3,4,4,5,5,3,3,4,4
%N A373607 Sum of the odd-indexed digits in the primorial base representation (A049345) of n.
%H A373607 Antti Karttunen, <a href="/A373607/b373607.txt">Table of n, a(n) for n = 0..16170</a>
%H A373607 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>
%F A373607 a(n) = A276150(n) - A373606(n).
%F A373607 a(n) = A373606(n) - A373605(n).
%e A373607 A049345(85) = 2401, and the sum of digits at the odd positions (with the rightmost digit having index 0) is 0+2 = 2, thus a(85) = 2.
%o A373607 (PARI) A373607(n) = { my(p=2, i=0, s=0); while(n, if(i%2, s += (n%p)); n = n\p; p = nextprime(1+p); i = !i); (s); };
%Y A373607 Cf. A049345, A276150, A373605, A373606.
%K A373607 nonn
%O A373607 0,5
%A A373607 _Antti Karttunen_, Jun 18 2024