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 A161825 a(n) is the GCD of n and {the number made by reversing the order of the digits of n written in binary}. 2
 1, 1, 3, 1, 5, 3, 7, 1, 9, 5, 1, 3, 1, 7, 15, 1, 17, 9, 1, 5, 21, 1, 1, 3, 1, 1, 27, 7, 1, 15, 31, 1, 33, 17, 7, 9, 1, 1, 3, 5, 1, 21, 1, 1, 45, 1, 1, 3, 7, 1, 51, 1, 1, 27, 1, 7, 3, 1, 1, 15, 1, 31, 63, 1, 65, 33, 1, 17, 3, 7, 1, 9, 73, 1, 15, 1, 1, 3, 1, 5, 3, 1, 1, 21, 85, 1, 3, 1, 1, 45, 1, 1, 93, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 EXAMPLE 70 in binary is 1000110. Reversing this (and ignoring the leading 0), we have 110001, which is 49 in decimal. Therefore a(70) = gcd(70,49) = 7. MAPLE A030101 := proc(n) local bdgs; bdgs := convert(n, base, 2) ; add( op(-i, bdgs)*2^(i-1), i=1..nops(bdgs)) ; end: A161825 := proc(n) gcd(A030101(n), n) ; end: seq(A161825(n), n=1..100) ; # R. J. Mathar, Jul 04 2009 MATHEMATICA Array[GCD[#, IntegerReverse[#, 2]] &, 94] (* Michael De Vlieger, Feb 24 2019 *) PROG (PARI) a(n) = gcd(n, fromdigits(Vecrev(binary(n)), 2)); \\ Michel Marcus, Feb 25 2019 CROSSREFS Cf. A030101. Sequence in context: A116528 A081431 A053641 * A099551 A211206 A330717 Adjacent sequences:  A161822 A161823 A161824 * A161826 A161827 A161828 KEYWORD base,nonn AUTHOR Leroy Quet, Jun 20 2009 EXTENSIONS Example corrected by Leroy Quet, Jun 21 2009 a(4) corrected and sequence extended by R. J. Mathar, Jul 04 2009 STATUS approved

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Last modified April 11 18:00 EDT 2021. Contains 342888 sequences. (Running on oeis4.)