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A261303
a(n+1) = abs(a(n) - gcd(a(n), 3n+2)), a(1) = 1.
1
1, 0, 8, 7, 0, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 71, 70, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9
OFFSET
1,3
COMMENTS
The absolute value is relevant only when a(n) = 0, in which case a(n+1) = gcd(a(n), 3n+2) = 3n+2.
It is conjectured that a(n) = 0 implies that 3n+2 = a(n+1) is prime, for all n > 2, cf. A186255. (This is the sequence {u(n)} mentioned there.)
PROG
(PARI) print1(a=1); for(n=1, 199, print1(", ", a=abs(a-gcd(a, 3*n+2))))
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Aug 14 2015
STATUS
approved