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A120094
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).
0
7, 15, 31, 63, 81, 127, 239, 255, 470, 511, 1023, 2047, 4095
OFFSET
1,1
COMMENTS
Apart from the (2^i-1)-th rows, there are no obvious divisibility properties that would explain the coincidence. '1' is the 0th row.
EXAMPLE
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.
PROG
(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, ", ")))
CROSSREFS
Cf. A007318.
Sequence in context: A179882 A317510 A137196 * A078485 A233297 A159695
KEYWORD
nonn,more
AUTHOR
Phil Carmody, Aug 15 2006
EXTENSIONS
Offset changed to 1 and a(11)-a(13) from Jinyuan Wang, Aug 23 2021
STATUS
approved