A288888 a(n) is the total number of elements in all sum-free subsets of {1,...,n}.

1, 2, 7, 12, 27, 45, 93, 144, 294, 428, 796, 1220, 2186, 3155, 5637, 8102, 13907, 20070, 33746, 47416, 81050, 112226, 184541, 260780, 421222, 577447, 947934, 1304821, 2087701, 2857024, 4535223, 6157288, 9878133, 13257735, 20790674, 28332734, 44304037, 59072318

Offset: 1

Author

Ben Burns, Jun 18 2017

Keywords

• nonn

Comments

a(n) is the sum of the n-th row of A288887.

Examples

			A288887 begins:
  1;
  1,  1;
  2,  2,  3;
  3,  2,  4,  3;
  5,  3,  7,  5,  7;
  ...
		

Links

• Fausto A. C. Cariboni, Table of n, a(n) for n = 1..76
• Eric Weisstein's World of Mathematics, Sum-Free Set

Crossrefs

Cf. A007865. Rows sums of triangle A288887.

Programs

PARI

sumfree(v) = {for(i=1, #v, for (j=1, i, if (setsearch(v, v[i]+v[j]), return (0)););); return (1);}
a(n) = {my(nb = 0); forsubset(n, s, if (#s && sumfree(Set(s)), nb += #s);); nb;} \\ Michel Marcus, Nov 08 2020