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Search: id:A133290
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| A133290 |
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Prime powers of the form (6n+1)^k. |
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+0
1
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| 7, 13, 19, 31, 37, 43, 49, 61, 67, 73, 79, 97, 103, 109, 127, 139, 151, 157, 163, 169, 181, 193, 199, 211, 223, 229, 241, 271, 277, 283, 307, 313, 331, 337, 343, 349, 361, 367, 373, 379, 397, 409, 421, 433, 439, 457, 463, 487, 499, 523, 541, 547, 571, 577, 601
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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1 + sum of the indices of the first two numbers in A003215 that are divisible by n if 1 + the sum of those indices equals n.
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LINKS
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Eric Weisstein's World of Mathematics, Hex Number.
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EXAMPLE
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A003215(1) = 7 is divisible by 7, A003215(5) = 91 is divisible by = 7, and 1+5+1=7, so 7 is a member.
A003215(5) = 91 is divisible by = 13, A003215(7) = 169 is divisible by = 13, and 5+7+1=13 so 13 is a member.
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PROGRAM
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(Excel cell formula) Generate the indices with: =if(mod(1+3*row()*(row()-1); 6*column()+1)=0; row(); ") Then sum the first two indices that equals the column.
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CROSSREFS
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Cf. A003215, A002476, subsequence of A000961.
Sequence in context: A129904 A088513 A004611 this_sequence A038590 A129389 A107925
Adjacent sequences: A133287 A133288 A133289 this_sequence A133291 A133292 A133293
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KEYWORD
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nonn
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AUTHOR
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Mats Granvik (mgranvik(AT)abo.fi), Oct 16 2007, Oct 20 2007
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