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A048332
Numbers that are repdigits in base 7.
4
0, 1, 2, 3, 4, 5, 6, 8, 16, 24, 32, 40, 48, 57, 114, 171, 228, 285, 342, 400, 800, 1200, 1600, 2000, 2400, 2801, 5602, 8403, 11204, 14005, 16806, 19608, 39216, 58824, 78432, 98040, 117648, 137257, 274514, 411771, 549028, 686285, 823542, 960800
OFFSET
0,3
LINKS
Eric Weisstein's World of Mathematics, Repdigit.
FORMULA
From Chai Wah Wu, May 30 2016: (Start)
a(n) = 8*a(n-6) - 7*a(n-12) for n > 11.
G.f.: x*(6*x^5 + 5*x^4 + 4*x^3 + 3*x^2 + 2*x + 1)/(7*x^12 - 8*x^6 + 1). (End)
a(n) = (n - 6*floor((n-1)/6))*(7^floor((n+5)/6) - 1)/6. - Ilya Gutkovskiy, May 30 2016
Sum_{n>=1} 1/a(n) = (147/10) * A248724 = 2.80637791743084519957... - Amiram Eldar, Jan 21 2022
MATHEMATICA
Union[Flatten[Table[FromDigits[PadRight[{}, n, d], 7], {n, 0, 40}, {d, 6}]]] (* Vincenzo Librandi, Feb 06 2014 *)
LinearRecurrence[{0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, -7}, {0, 1, 2, 3, 4, 5, 6, 8, 16, 24, 32, 40}, 25] (* G. C. Greubel, May 30 2016 *)
PROG
(Python)
A048332_list = [0] + [int(d*l, 7) for l in range(1, 10) for d in '123456'] # Chai Wah Wu, May 30 2016
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Patrick De Geest, Feb 15 1999
STATUS
approved