A167188 Smaller prime power associated with record gap in A167186.

1, 4, 9, 16, 32, 81, 128, 169, 361, 1024, 1369, 2401, 4489, 5329, 6889, 8192, 12769, 19683, 32768, 39601, 44521, 85849, 177241, 218089, 262144, 279841, 436921, 597529, 744769, 786769, 1142761, 1771561, 5340721, 6135529, 8826841, 10699441, 17447329, 18464209

Offset

1,2

Links

Donovan Johnson, Table of n, a(n) for n = 1..200

Example

32 is in the sequence since the gap between 32 and the next prime power, 49, is greater than any previous gap.

Prog

(PARI) isA025475(n) = (omega(n) == 1 & !isprime(n)) | (n == 1)
d_max=0; n_prev=1; for(n=2, 32e6, if(isA025475(n), d=n-n_prev; if(d>d_max, print(n_prev); d_max=d); n_prev=n))

Crossrefs

Larger prime power: A167189.

Record gaps between nonprime prime powers: A167186.

Gaps between nonprime prime powers: A053707.

List of nonprime prime powers: A025475.

Sequence in context: A007679 A239870 A068037 * A295720 A349800 A296152

Adjacent sequences: A167185 A167186 A167187 * A167189 A167190 A167191

Keyword

nonn

Author

Michael B. Porter, Nov 01 2009

Status

approved