OFFSET
0,2
COMMENTS
First bisection of A219191. - Bruno Berselli, Nov 15 2012
LINKS
FORMULA
a(n) = a(n-1) + 14*n - 6 with n>0, a(0)=0. - Vincenzo Librandi, Nov 17 2010
EXAMPLE
From Bruno Berselli, Oct 27 2017: (Start)
After 0:
8 = -(1) + (2+3+4).
30 = -(1+2) + (3+4+5+6+7+8).
66 = -(1+2+3) + (4+5+6+7+8+9+10+11+12).
116 = -(1+2+3+4) + (5+6+7+8+9+10+11+12+13+14+15+16). (End)
PROG
(PARI) a(n)=7*n^2+n \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Evgeniy A. Chukhlomin (dkea(AT)yandex.ru), Feb 18 2004
STATUS
approved