OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..10011
FORMULA
Write down triangle with rows 1; 2, 3; 4, 5, 6; 7, 8, 9, 10; ...; read rows alternately from right and left ends.
PROG
(PARI) { n=0; for (i = 1, 141, d=i; s=1; for (j=1, i, if (j==1, a=(i^2 + i)/2, a+=s*d); write("b059399.txt", n++, " ", a); d--; s=-s; ); ) } \\ Harry J. Smith, Jun 26 2009
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Robert G. Wilson v, Jan 29 2001
STATUS
approved