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 A134736 a(1) = 5; for n >1, a(n) = a(n-1) + gcd(n, a(n-1)). 8
 5, 6, 9, 10, 15, 18, 19, 20, 21, 22, 33, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 69, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 141, 144, 145, 150, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Eric S. Rowland, A simple prime-generating recurrence, Abstracts Amer. Math. Soc., 29 (No. 1, 2008), p. 50 (Abstract 1035-11-986). LINKS T. D. Noe, Table of n, a(n) for n=1..1000 Eric S. Rowland, A simple prime-generating recurrence. MATHEMATICA a[1] = 5; a[n_] := a[n] = a[n-1] + GCD[n, a[n-1]]; Array[a, 66] (* Jean-François Alcover, Oct 01 2018 *) RecurrenceTable[{a[1]==5, a[n]==a[n-1]+GCD[n, a[n-1]]}, a, {n, 70}] (* Harvey P. Dale, Nov 24 2018 *) PROG (Haskell) a134736 n = a134736_list !! (n-1) a134736_list =    5 : zipWith (+) a134736_list (zipWith gcd a134736_list [2..]) -- Reinhard Zumkeller, Nov 15 2013 CROSSREFS See A106108 for other cross-references. Cf. A230504, A134743 (first differences), A084662, A084663. Sequence in context: A188191 A117827 A246784 * A285505 A220968 A179662 Adjacent sequences:  A134733 A134734 A134735 * A134737 A134738 A134739 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 28 2008 STATUS approved

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Last modified January 22 15:57 EST 2019. Contains 319364 sequences. (Running on oeis4.)