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A176069 Products of two distinct primes of the form n^2+n+1. 2
21, 57, 91, 111, 133, 183, 381, 553, 703, 813, 871, 993, 1057, 1191, 1261, 1333, 1561, 1641, 1807, 1893, 1981, 2071, 2257, 2353, 2653, 2757, 2863, 3193, 3661, 4033, 4291, 4971, 5257, 5403, 5853, 6807, 6973, 7141, 7311, 7483, 8373, 8557, 8743, 9121, 9313 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

21=3*7=4^2+4+1,...

LINKS

Table of n, a(n) for n=1..45.

MATHEMATICA

f[n_]:=Last/@FactorInteger[n]=={1, 1}; Select[Array[ #^2+#+1&, 6!, 2], f[ # ]&]

CROSSREFS

Cf. A174969,

Sequence in context: A257103 A146560 A174969 * A043382 A044123 A044504

Adjacent sequences:  A176066 A176067 A176068 * A176070 A176071 A176072

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Apr 07 2010

STATUS

approved

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Last modified May 22 06:54 EDT 2022. Contains 353933 sequences. (Running on oeis4.)