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Search: id:A064385
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| 7, 47, 247, 1247, 6247, 31247, 156247, 781247, 3906247, 19531247, 97656247, 488281247, 2441406247, 12207031247, 61035156247, 305175781247, 1525878906247, 7629394531247, 38146972656247
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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5-th polygonal numbers for polygons of 5^n sides divided by 5: p(5,5^x)/5, where p(n,k)=(n/2)*(n*k-k+4-2*n).
This sequence exhibits periodic digit repetition; e.g. the last digit repeats as 7, the penultimate as 4, and the antepenultimate as 2, all with a period of 1; the fourth-to-last digit repeats the sequence 1, 6 with a period of 2; the fifth-to-last repeats the sequence 3, 5, 8, 0; the sixth-to-last repeats 1, 7, 9, 5, 6, 2, 4, 0. And so on, it seems, for the other digits as the numbers grow.
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MAPLE
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p := proc(n, k) (n/2)*(n*k-k+4-2*n) end: for x from 1 to 19 do p(5, 5^x)/5 od; q := proc(x) 2*5^x-3 end: for x from 1 to 19 do q(x) od;
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PROGRAM
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(PARI) p(n, k) = (n/2)*(n*k-k+4-2*n) for(x=1, 19, print(p(5, 5^x)/5)) q(x) = 2*5^x-3 for(x=1, 19, print(q(x)))
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CROSSREFS
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Sequence in context: A009202 A093112 A091516 this_sequence A009260 A126635 A085352
Adjacent sequences: A064382 A064383 A064384 this_sequence A064386 A064387 A064388
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KEYWORD
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nonn,easy
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AUTHOR
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Daniel Dockery (drd(AT)peritus.virtualave.net), Sep 16, 2001
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