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A065728
Partition numbers (A000041) that are semiprimes (A001358).
4
15, 22, 77, 1255, 2012558, 2679689, 9289091, 18004327, 38887673, 56634173, 72533807, 82010177, 104651419, 2056148051, 2552338241, 20390982757, 27517052599, 118159068427, 749474411781, 5134205287973, 18028182516671
OFFSET
1,1
COMMENTS
Enoch Haga asks if this is a finite sequence. The larger these numbers get, the more opportunity for more factors.
LINKS
Hisanori Mishima, Factorization results
Eric Weisstein's World of Mathematics, Semiprime.
FORMULA
A064911(a(n))*A167392(a(n)) = 1. [From Reinhard Zumkeller, Nov 03 2009]
EXAMPLE
E.g., the 808th partition number 8151756509675604512522473567 = 5963320232189 * 1366982853893003.
MATHEMATICA
Select[PartitionsP[Range[0, 450]], PrimeOmega[#]==2&] (* Harvey P. Dale, Sep 19 2016 *)
PROG
(PARI) { n=0; for (m=1, 10^9, p=numbpart(m); if (bigomega(p) == 2, write("b065728.txt", n++, " ", p); if (n==100, return)) ) } \\ Harry J. Smith, Oct 28 2009
CROSSREFS
Intersection of A001358 and A000041.
Sequence in context: A018889 A186525 A236107 * A344134 A241253 A317793
KEYWORD
nonn
AUTHOR
Patrick De Geest, Nov 18 2001
EXTENSIONS
OFFSET changed from 0,1 to 1,1 by Harry J. Smith, Oct 28 2009
STATUS
approved