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 A064541 Numbers k such that 2^k ends in k. 15
 36, 736, 8736, 48736, 948736, 2948736, 32948736, 432948736, 3432948736, 53432948736, 353432948736, 5353432948736, 75353432948736, 5075353432948736, 15075353432948736, 615075353432948736, 8615075353432948736, 98615075353432948736, 8098615075353432948736, 38098615075353432948736 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS There is no term with 15 digits. LINKS FORMULA a(n+1) is a suffix of 2^a(n) formed by a nonzero digit followed by a number of zeros and a(n). E.g., a(13)=75353432948736 and 2^a(13) ends with ...15075353432948736, hence a(14)=5075353432948736. - Max Alekseyev, Apr 18 2007 Can be obtained from A109405 by removing all repeats. - Max Alekseyev, May 11 2007 EXAMPLE 2^36 = 68719476736 which ends in 36. MATHEMATICA a[1] = 36; a[n_] := a[n] = For[ida = IntegerDigits[a[n-1]]; k = 1, True, k++, idk = IntegerDigits[k]; pm = PowerMod[2, an = FromDigits[Join[idk, ida]], 10^IntegerLength[an]]; If[pm == an, Return[an]]]; Array[a, 20] (* Jean-François Alcover, Feb 15 2018 *) CROSSREFS Cf. A121319, A109405, A206636. The leading digits are listed in A064540. Digits read backwards form A133612. Sequence in context: A138832 A223998 A109405 * A058001 A004329 A089909 Adjacent sequences:  A064538 A064539 A064540 * A064542 A064543 A064544 KEYWORD base,nonn,nice AUTHOR Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 08 2001 STATUS approved

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Last modified October 23 14:54 EDT 2019. Contains 328345 sequences. (Running on oeis4.)