A168270 Squarefree numbers which are also isolated numbers.

2, 6, 23, 30, 37, 42, 47, 53, 67, 79, 83, 89, 97, 102, 113, 127, 131, 138, 157, 163, 167, 173, 211, 223, 233, 251, 257, 263, 277, 282, 293, 307, 317, 331, 337, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 439, 443, 449, 457, 462, 467, 479, 487, 491, 499, 503, 509

Offset

1,1

Links

Table of n, a(n) for n=1..57.

Formula

A005117 INTERSECT A167706.

A005117 \ A168252.

Maple

isA007510 := proc(n) if isprime(n) then not isprime(n-2) and not isprime(n+2) ; else false; end if ; end proc:
isA014574 := proc(n) isprime(n+1) and isprime(n-1) ; end proc:
isA167706 := proc(n) isA007510(n) or isA014574(n) ; end proc:
isA005117 := proc(n) n =1 or numtheory[issqrfree](n) ; end proc:
isA168270 := proc(n) isA005117(n) and isA167706(n) ; end proc:
for n from 1 to 600 do if isA168270(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Dec 09 2009

Crossrefs

Cf. A005117, A167706, A168252.

Sequence in context: A264173 A220183 A177252 * A222761 A298817 A245125

Adjacent sequences: A168267 A168268 A168269 * A168271 A168272 A168273

Keyword

nonn

Author

Juri-Stepan Gerasimov, Nov 22 2009

Extensions

Corrected (missing terms inserted) by R. J. Mathar, Dec 09 2009

Status

approved