A130903 Bad primes (version 2). Primes not in A028388.

2, 3, 7, 13, 19, 23, 31, 43, 47, 61, 73, 79, 83, 89, 103, 107, 109, 113, 131, 137, 139, 151, 157, 163, 167, 173, 181, 193, 197, 199, 211, 229, 233, 239, 241, 263, 271, 277, 281, 283, 293, 313, 317, 337, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 421

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Formula

{p in A000040 and p not in A028388}.

Maple

isA028388 := proc(p) local a, n, pmin, pplu; if isprime(p) then a := true ; if p < 5 then RETURN(false) ; fi ; pmin := p ; pplu := p ; while pmin > 2 do pmin := prevprime(pmin) ; pplu := nextprime(pplu) ; if p^2 <= pmin*pplu then a := false ; break ; fi ; od: RETURN(a) ; else RETURN(false) ; fi ; end: isA130903 := proc(p) if not isprime(p) then RETURN(false) ; else RETURN(not isA028388(p)) ; fi ; end: for i from 1 to 100 do p := ithprime(i) ; if isA130903(p) then printf("%d, ", p) ; fi ; od: # R. J. Mathar, Sep 02 2007

Crossrefs

Cf. A000040, A028388, A046869, A068828.

Sequence in context: A155479 A019411 A105792 * A068828 A100764 A076974

Adjacent sequences: A130900 A130901 A130902 * A130904 A130905 A130906

Keyword

easy,nonn

Author

Jonathan Vos Post, Aug 22 2007

Extensions

Corrected and extended by R. J. Mathar, Sep 02 2007

Status

approved