OFFSET
1,3
COMMENTS
P_7(i) = the i-th heptagonal number.
LINKS
Douglas E. Iannucci and Donna Mills-Taylor. On Generalizing the Connell Sequence. Journal of Integer Sequences 2 (1999), Article 99.1.7.
Grady D. Bullington, The Connell Sum Sequence, J. Integer Seq. 10 (2007), Article 07.2.6. (includes direct formula for a(n))
FORMULA
a(n) = A045930(n)-n+1.
PROG
(PARI) isHeptag(n) = {if (! issquare(40*n+9, &res), return (0)); if ((res + 3) % 10, return (0), return (1)); }
lista(m) = {aa = 1; for (i=1, m, print1(aa, ", "); if (! isHeptag(i), aa += 2); ); } \\ Michel Marcus, Apr 01 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Grady Bullington (bullingt(AT)uwosh.edu), Sep 14 2006
EXTENSIONS
Definition corrected by Michel Marcus, Apr 01 2013
STATUS
approved