A076120 a(n) = smallest multiple of n other than n which is relatively prime to both a(n-1) and a(n+1).

3, 4, 9, 8, 25, 12, 35, 16, 27, 20, 77, 24, 65, 28, 45, 32, 85, 36, 133, 40, 63, 44, 115, 48, 125, 52, 81, 56, 319, 60, 217, 64, 99, 68, 175, 72, 185, 76, 117, 80, 451, 84, 215, 88, 135, 92, 235, 96, 343, 100, 153, 104, 265, 108, 275, 112, 171, 116, 413, 120, 427

Offset

0,1

Links

Table of n, a(n) for n=0..60.

Example

a(1)=3 and is not 2 else there is no candidate for a(2). Similarly a(5) is not 15 so that a(6) exists.

Prog

(PARI) p=3:print1("3, "):for(n=2, 80, for(k=2, 10^9, if(gcd(k*n, p)==1&&gcd(k, n+1)==1, print1(k*n", "):p=k*n:break)))

Crossrefs

Sequence in context: A372121 A305551 A306018 * A082188 A202499 A341319

Adjacent sequences: A076117 A076118 A076119 * A076121 A076122 A076123

Keyword

nonn

Author

Amarnath Murthy, Oct 14 2002

Extensions

More terms from Ralf Stephan, Mar 27 2003

Status

approved