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A067844 Numbers k such that k and 2^k end with the same digit. 4
14, 16, 34, 36, 54, 56, 74, 76, 94, 96, 114, 116, 134, 136, 154, 156, 174, 176, 194, 196, 214, 216, 234, 236, 254, 256, 274, 276, 294, 296, 314, 316, 334, 336, 354, 356, 374, 376, 394, 396, 414, 416, 434, 436, 454, 456, 474, 476, 494, 496, 514, 516, 534, 536 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers k such that k and (2^(2*h+1))^k (for n>=0) end with the same digit. - Bruno Berselli, Dec 13 2018

LINKS

Table of n, a(n) for n=1..54.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

From Colin Barker, Dec 01 2012: (Start)

G.f.: 2*x*(2*x^2 + x + 7)/((x - 1)^2*(x + 1)).

a(n) = a(n-1) + a(n-2) - a(n-3).

a(n) = 10*n - 4*(-1)^n. (End)

EXAMPLE

2^36 = 68719476736 hence 36 is in the sequence.

PROG

(PARI) isok(n) = (2^n - n) % 10 == 0; \\ Michel Marcus, Nov 23 2013

CROSSREFS

Cf. A064541.

Sequence in context: A175887 A305885 A224402 * A015877 A192290 A152010

Adjacent sequences:  A067841 A067842 A067843 * A067845 A067846 A067847

KEYWORD

nonn,base,easy

AUTHOR

Benoit Cloitre, Mar 07 2002

EXTENSIONS

Example corrected by Michel Marcus, Nov 23 2013

STATUS

approved

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Last modified March 8 01:41 EST 2021. Contains 341934 sequences. (Running on oeis4.)