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A095842
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Prime powers having no partition into two prime powers.
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5
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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
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OFFSET
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1,2
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COMMENTS
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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
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LINKS
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PROG
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(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)
(Haskell)
a095842 n = a095842_list !! (n-1)
a095842_list = filter ((== 0) . a071330) a000961_list
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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