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A173297
Numbers k such that exactly one of k^2 + k - 1 and k^2 + k + 1 is prime.
1
1, 4, 9, 10, 11, 12, 13, 14, 16, 17, 19, 26, 27, 28, 30, 31, 33, 35, 39, 44, 45, 46, 48, 53, 55, 56, 57, 60, 62, 64, 65, 68, 69, 70, 71, 75, 76, 77, 78, 80, 83, 85, 86, 90, 93, 94, 96, 99, 100, 103, 105, 110, 111, 114, 115, 117, 119, 120, 125, 126, 130, 134, 140, 143, 144
OFFSET
1,2
COMMENTS
Numbers k such that either k-th oblong number-+1 is prime.
Indices k such that A002378(k)+1 or A002378(k)-1 is prime, but not both. -R. J. Mathar, Feb 21 2010
LINKS
MAPLE
isA173297 := proc(n) local p, pplus, pmin ; pmin := isprime(n*(1+n)-1) ; pplus := isprime(n*(1+n)+1) ; if pmin <> pplus then return true; else return false; end if; end proc: for n from 1 to 300 do if isA173297(n) then printf("%d, ", n) ; end if; end do ; # R. J. Mathar, Feb 21 2010
CROSSREFS
Sequence in context: A088037 A071768 A301478 * A161913 A020673 A166498
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
46 and 86 inserted by R. J. Mathar, Feb 21 2010
Edited by Charles R Greathouse IV, Mar 24 2010
STATUS
approved