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).

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.

Links

Table of n, a(n) for n=1..13.

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

Adjacent sequences: A120091 A120092 A120093 * A120095 A120096 A120097

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