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A095842
Prime powers having no partition into two prime powers.
5
1, 149, 331, 373, 509, 701, 757, 809, 877, 907, 997, 1019, 1087, 1259, 1549, 1597, 1619, 1657, 1759, 1777, 1783, 1867, 1973, 2293, 2377, 2503, 2579, 2683, 2789, 2843, 2879, 2909, 2999, 3119, 3163, 3181, 3187, 3299, 3343, 3433, 3539, 3643
OFFSET
1,2
COMMENTS
A095840(A095874(a(n))) = 0.
A071330(a(n)) = 0.
Here, "prime powers" is used in the relaxed sense, including 1. The numbers 96721, 121801, 192721, 205379, 226981,... seem to be the smallest composite terms of this sequence, which establishes the difference with the subsequence A115231. - M. F. Hasler, Nov 20 2014
LINKS
PROG
(PARI) isprimepower(n)=ispower(n, , &n); isprime(n)||n==1;
isA095842(n)=if(!isprimepower(n), return(0)); forprime(p=2, n\2, if(isprimepower(n-p), return(0))); forprime(p=2, sqrtint(n\2), for(e=1, log(n\2)\log(p), if(isprimepower(n-p^e), return(0)))); !isprimepower(n-1)
\\ Charles R Greathouse IV, Jul 06 2011
(Haskell)
a095842 n = a095842_list !! (n-1)
a095842_list = filter ((== 0) . a071330) a000961_list
-- Reinhard Zumkeller, Jan 11 2013
CROSSREFS
Subsequence of A071331.
Sequence in context: A244661 A146137 A071331 * A142359 A185692 A216312
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jun 10 2004
STATUS
approved