%I #11 Aug 23 2021 06:11:06
%S 7,15,31,63,81,127,239,255,470,511,1023,2047,4095
%N Rows of Pascal's triangle which contain no terms numerically adjacent to odd primes (the 1's at either end are of course numerically adjacent to the even prime 2).
%C Apart from the (2^i-1)-th rows, there are no obvious divisibility properties that would explain the coincidence. '1' is the 0th row.
%e The 7th, 15th, 31st, ... (2^i-1)-th rows are all included as Pascal's triangle only contains odd terms, thus all numerically adjacent terms are even.
%o (PARI) for(n=2, 1000, for(k=1, n\2, ok=1; c=binomial(n, k); if(ispseudoprime(c+1)||ispseudoprime(c-1), ok=0; break; )); if(ok,print1(n, ", ")))
%Y Cf. A007318.
%K nonn,more
%O 1,1
%A _Phil Carmody_, Aug 15 2006
%E Offset changed to 1 and a(11)-a(13) from _Jinyuan Wang_, Aug 23 2021