cp's OEIS Frontend

A067185 Numbers k such that prime(k+1) + prime(k) == 1 (mod k).

%I A067185 #25 Feb 17 2021 04:18:07
%S A067185 1,7,17,109,281,1669,6592663,16899113,16899145,16899295,749973611,
%T A067185 5067034877,5067034925,34487825911,1626582230375
%N A067185 Numbers k such that prime(k+1) + prime(k) == 1 (mod k).
%t A067185 a = b = 0; Do[b = Prime[n + 1]; If[Mod[a + b, n] == 1, Print[n]]; a = b, {n, 1, 10^9}]
%o A067185 (Sage)
%o A067185 def A067185(max):
%o A067185     terms = []
%o A067185     p = 2
%o A067185     for n in range(1, max + 1):
%o A067185         q = next_prime(p)
%o A067185         if not (p + q - 1) % n:
%o A067185             terms.append(n)
%o A067185         p = q
%o A067185     return terms
%o A067185 # _Eric M. Schmidt_, Feb 05 2013
%o A067185 (PARI) isok(k) = (prime(k+1) + prime(k)) % k == 1; \\ _Michel Marcus_, Feb 17 2021
%Y A067185 Cf. A066895 (== 0 instead of 1).
%K A067185 nonn,more
%O A067185 1,2
%A A067185 _Benoit Cloitre_, Feb 19 2002
%E A067185 Edited and extended by _Robert G. Wilson v_, Feb 19 2002
%E A067185 Extended by _David W. Wilson_, Feb 20 2002
%E A067185 a(11)-a(14) from _Donovan Johnson_, Mar 10 2010
%E A067185 First term from _Eric M. Schmidt_, Feb 05 2013