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 A236866 #18 Aug 07 2025 14:48:20 %S A236866 2,3,4,5,6,7,8,9,10,11,12,13,15,16,17,18,19,20,22,23,24,26,27,28,29, %T A236866 30,31,34,35,37,38,40,41,42,44,45,47,48,49,51,52,53,54,57,60,61,62,63, %U A236866 64,65,67,69,71,72,73,74,75,76,79,82,83,84,85,89,90,93,94,95 %N A236866 Positions of primes in A007775 (numbers not divisible by 2, 3 or 5). %C A236866 From _Antti Karttunen_, Feb 01 2014: (Start) %C A236866 Positions of primes among natural numbers coprime to 30. %C A236866 Term 1 is missing from the sequence, because A007775(1)=1 is not considered a prime, terms 2 - 13 are all present, and 14 is the next term missing from here, as A007775(14)=49 is the first composite in that sequence. %C A236866 (End) %H A236866 Antti Karttunen, <a href="/A236866/b236866.txt">Table of n, a(n) for n = 1..10000</a> %o A236866 (Python) %o A236866 from sympy import isprime %o A236866 i=0 %o A236866 for n in range(1000): %o A236866 if n%2 and n%3 and n%5: %o A236866 i+=1 # A007775(i)=n %o A236866 if isprime(n): print(i, end=', ') %o A236866 (Scheme) %o A236866 ;; With Antti Karttunen's IntSeq-library. %o A236866 (define A236866 (MATCHING-POS 1 1 (lambda (n) (prime? (A007775 n))))) %o A236866 ;; Where a slow version of A007775 can be defined for example like this, %o A236866 (define A007775 (MATCHING-POS 1 1 (lambda (n) (= 1 (gcd n 30))))) %o A236866 ;; from _Antti Karttunen_, Feb 01 2014 %Y A236866 Cf. A007775, A181709. %K A236866 nonn,easy %O A236866 1,1 %A A236866 _Alex Ratushnyak_, Jan 31 2014