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A130903 Bad primes (version 2). Primes not in A028388. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 18 05:08 EST 2017. Contains 294853 sequences.