A261303 a(n+1) = abs(a(n) - gcd(a(n), 3n+2)), a(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.)

Links

Table of n, a(n) for n=1..80.

Prog

(PARI) print1(a=1); for(n=1, 199, print1(", ", a=abs(a-gcd(a, 3*n+2))))

Crossrefs

Cf. A261301 - A261310, A186253 - A186263, A106108.

Sequence in context: A369633 A294969 A292821 * A259348 A257238 A348728

Adjacent sequences: A261300 A261301 A261302 * A261304 A261305 A261306

Keyword

nonn

Author

M. F. Hasler, Aug 14 2015

Status

approved