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A104006
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Primes of the form 2*p*q+1, where p and q are (not necessarily distinct) odd primes.
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1
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19, 31, 43, 67, 71, 79, 103, 131, 139, 191, 223, 239, 283, 311, 367, 419, 431, 439, 443, 499, 599, 607, 619, 643, 647, 659, 683, 743, 787, 823, 827, 907, 947, 971, 1031, 1039, 1087, 1091, 1103, 1163, 1223, 1259, 1399, 1427, 1447, 1499, 1511, 1543, 1559, 1571
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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EXAMPLE
| 19 = 2*3*3 + 1.
31 = 2*3*5 + 1.
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MATHEMATICA
| Select[Prime[Range[3, 500]], FactorInteger[(# - 1)/2][[1, 1]] > 2 && Sum[FactorInteger[(# - 1)/2][[i, 2]], {i, 1, Length[FactorInteger[(# - 1)/2]]}] == 2 &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Sep 26 2007
Take[ Select[ Sort[ Flatten[ Table[ 2Prime[p]Prime[q] + 1, {p, 47}, {q, p}]]], PrimeQ[ # ] &], 50] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 06 2005)
Select[Prime[Range[19, 500]], OddQ[ (#-1)/2]&&3==Plus@@Last/@FactorInteger[ #-1]&] - Zak Seidov, Sep 26 2007
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CROSSREFS
| Sequence in context: A043298 A040068 A096787 * A117065 A006035 A104485
Adjacent sequences: A104003 A104004 A104005 * A104007 A104008 A104009
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KEYWORD
| easy,nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Mar 31 2005
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EXTENSIONS
| Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 06 2005.
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