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Search: id:A134407
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| A134407 |
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Numbers n such that n^2 + 1 is a composite number. |
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+0
1
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| 3, 5, 7, 8, 9, 11, 12, 13, 15, 17, 18, 19, 21, 22, 23, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(1)=3, because 3^2 + 1 = 10 is a composite number,
a(2)=5, because 5^2 + 1 = 26 is a composite number,
a(3)=7, becasue 7^2 + 1 = 50 is composite.
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MAPLE
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ts_fn2:=proc(n) local i, tren, ans; ans:=[ ]: for i from 1 to n do tren := i^(2)+1: if (isprime(tren) = false) then ans:=[ op(ans), i ]: fi od: RETURN(ans) end: ts_fn2(200);
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CROSSREFS
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Cf. A002496, A005574.
Sequence in context: A025051 A020884 A024352 this_sequence A144724 A060462 A072668
Adjacent sequences: A134404 A134405 A134406 this_sequence A134408 A134409 A134410
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KEYWORD
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nonn
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AUTHOR
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Jani Melik (jani_melik(AT)hotmail.com), Jan 18 2008
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