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A181287
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Numbers of the form i*5^j-1 (i=1..4, j >= 0).
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10
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0, 1, 2, 3, 4, 9, 14, 19, 24, 49, 74, 99, 124, 249, 374, 499, 624, 1249, 1874, 2499, 3124, 6249, 9374, 12499, 15624, 31249, 46874, 62499, 78124, 156249, 234374, 312499, 390624, 781249, 1171874, 1562499, 1953124, 3906249, 5859374, 7812499, 9765624, 19531249, 29296874, 39062499, 48828124, 97656249, 146484374, 195312499
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OFFSET
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1,3
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COMMENTS
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Row numbers of Pascal's Triangle where none of the binomial coefficients in that row is divisible by 5. - Thomas M. Green, Apr 02 2013
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LINKS
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FORMULA
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a(n) = a(n-1)+5*a(n-4)-5*a(n-5). G.f.: x^2*(x+1)*(x^2+1) / ((x-1)*(5*x^4-1)). [Colin Barker, Feb 01 2013]
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EXAMPLE
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For n = 7, a(7) = 14 and the binomial coefficients in the 14th row of Pascal's Triangle are 1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1 and none of the elements in that row is divisible by 5. - Thomas M. Green, Apr 05 2013
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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