OFFSET
1,2
FORMULA
a(n) = ceiling((1+sqrt(24*n+1))/6) = floor((7+sqrt(24*n-23))/6).
PROG
(PARI) a(n) = (7+sqrt(24*n-23))\6; \\ Michel Marcus, Oct 30 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Daniele Parisse, Jun 02 2003, Jul 07 2007
STATUS
approved