cp's OEIS Frontend

A191350 The number of bases not exceeding n+1 in which the expansion of n (i) has only digits <=9 and (ii) represents a prime if digits are concatenated/reinterpreted as decimals.

%I A191350 #18 May 13 2013 01:54:20
%S A191350 1,2,1,3,1,3,2,2,3,3,2,4,2,4,4,5,3,7,4,6,6,8,4,7,5,6,6,8,4,9,4,9,7,7,
%T A191350 4,11,5,9,6,8,4,13,4,8,7,10,5,10,5,8,7,9,4,14,5,8,8,11,4,12,4,10,8,8,
%U A191350 5,15,6,8,6,13,4,14,5,10,6,8,6,17,5,8,7,12,6,13,5,11,8,11,4,15,5
%N A191350 The number of bases not exceeding n+1 in which the expansion of n (i) has only digits <=9 and (ii) represents a prime if digits are concatenated/reinterpreted as decimals.
%H A191350 Charles R Greathouse IV, <a href="/A191350/b191350.txt">Table of n, a(n) for n = 2..10000</a>
%e A191350 In bases 6, 8, 12 and 14 the digits of n=15 are 15_6=23, 15_8=17, 15_12=13, and 15_14=11. Since in other bases<=16 the expansions of 15 converted to decimal are not primes, a(15)=4.
%o A191350 (PARI) a(n)=my(m,t,k,i);sum(b=2,n+1,k=n;m=0;i=0;while(k,t=k%b;if(t>9,m=0;break);m+=10^i*t;i++;k\=b);isprime(m)) \\ _Charles R Greathouse IV_, Jun 01 2011
%Y A191350 Cf. A191291, A191322.
%K A191350 nonn,base
%O A191350 2,2
%A A191350 _Vladimir Shevelev_, May 31 2011
%E A191350 a(16)-a(91) from _Charles R Greathouse IV_, Jun 01 2011