OFFSET
1,2
COMMENTS
Based on testing the first 1000 primes of the form 3n-1, it seems that A003627 is a subsequence.
LINKS
Ivan N. Ianakiev, Table of n, a(n) for n = 1..10000
MATHEMATICA
next[n_, m_]:=Piecewise[{
{(k=m+1; While[!CoprimeQ[k, n]||!CoprimeQ[k, m], k++]; k), AllTrue[{n, m}, EvenQ]},
{m+2, OddQ[n]&&EvenQ[m]}, {m+1, EvenQ[n]&&OddQ[m]}}];
a[1]=1; a[2]=2; a[n_]:=a[n]=next[a[n-2], a[n-1]]; a/@Range[100]
PROG
(PARI) { for (v=1, 122, if (v<=2 || ((gcd(pp, p)==1) + (gcd(p, v)==1) + (gcd(v, pp)==1))==2, print1 (v", "); [pp, p]=[p, v])) } \\ Rémy Sigrist, May 01 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Ivan N. Ianakiev, Apr 29 2022
STATUS
approved
