A185708 - OEIS

%I #16 Aug 11 2019 11:47:51

%S 0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%T 0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,

%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0

%N Characteristic function of positive numbers that are primes ending in 7.

%H Antti Karttunen, <a href="/A185708/b185708.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%t Table[If[PrimeQ[n]&&Mod[n,10]==7,1,0],{n,120}] (* _Harvey P. Dale_, Aug 11 2019 *)

%o (PARI) A185708(n) = ((7==(n%10))&&isprime(n)); \\ _Antti Karttunen_, Oct 09 2018

%Y Cf. A030432 (primes of form 10n+7).

%K base,nonn

%O 1

%A _N. J. A. Sloane_, Feb 10 2011