A152076 a(n) = the largest prime p < prime(n) such that prime(n) - p is squarefree, where prime(n) is the n-th prime. a(n) = 0 if no such prime p exists.
2, 3, 5, 5, 11, 11, 17, 17, 23, 29, 31, 31, 41, 41, 47, 53, 59, 61, 61, 71, 73, 73, 83, 83, 79, 101, 101, 107, 107, 113, 109, 131, 137, 139, 149, 151, 157, 157, 167, 173, 179, 181, 191, 191, 197, 197, 197, 197, 227, 227, 233, 239, 241, 251, 257, 263, 269, 271, 271
Offset: 2
Keywords
Links
- Michael De Vlieger, Table of n, a(n) for n = 2..10000
Programs
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Mathematica
Table[NestWhile[NextPrime[#, -1] &, p, ! SquareFreeQ[# - p] &], {p, Prime@ Range[2, 10^4]}] (* Michael De Vlieger, Oct 30 2017, after Harvey P. Dale at A152075 *) -
PARI
A152076(n) = local(q=n=prime(n)); while( q=precprime(q-1), issquarefree(n-q) && return(q)) \\ M. F. Hasler, Nov 23 2008
Extensions
Terms beyond a(13) from M. F. Hasler and Ray Chandler, Nov 23 2008
Comments