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A037461 a(n)=Sum{d(i)*7^i: i=0,1,...,m}, where Sum{d(i)*4^i: i=0,1,...,m} is the base 4 representation of n. 4
1, 2, 3, 7, 8, 9, 10, 14, 15, 16, 17, 21, 22, 23, 24, 49, 50, 51, 52, 56, 57, 58, 59, 63, 64, 65, 66, 70, 71, 72, 73, 98, 99, 100, 101, 105, 106, 107, 108, 112, 113, 114, 115, 119, 120, 121, 122, 147, 148, 149, 150, 154, 155, 156, 157 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A number k is a term of this sequence if and only if 7 divides neither C(2*k-1,k) nor C(2*k,k).

LINKS

Clark Kimberling, Table of n, a(n) for n = 1..1000

EXAMPLE

39 = 3*1 + 1*4 + 2*4^2 -> 3*1 + 1*7 + 3*7^2 = 108, so a(39) = 108. - Clark Kimberling, Jul 30 2012

MATHEMATICA

Table[FromDigits[RealDigits[n, 4], 7], {n, 1, 100}]

(* Clark Kimberling, Aug 02 2012 *)

CROSSREFS

Cf. A050608.

Sequence in context: A154432 A251391 A047361 * A284514 A268398 A249587

Adjacent sequences:  A037458 A037459 A037460 * A037462 A037463 A037464

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified June 12 21:39 EDT 2021. Contains 344968 sequences. (Running on oeis4.)