A156838 Row sums of triangle A156837.

1, 3, 3, 7, 3, 13, 3, 17, 11, 17, 3, 51, 3, 21, 37, 55, 3, 83, 3, 113, 63, 29, 3, 271, 75, 33, 103, 223, 3, 453, 3, 329, 139, 41, 427, 897, 3, 45, 189, 1265, 3, 1267, 3, 651, 1277, 53, 3, 2943, 929, 1571, 313, 1001, 3, 3147, 2009, 4843, 387, 65, 3, 9159, 3, 69, 6541, 5459, 3647, 6753, 3, 2053, 559, 15299, 3, 25677, 3, 81

Offset: 1

Author

Gary W. Adamson & Mats Granvik, Feb 16 2009

Keywords

• nonn
• easy

Comments

a(n) = 3 iff n is prime.

Examples

			a(4) = 7 since row 4 of triangle A156837 = (3, 3, 0, 1).
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

A156837

Programs

Maple

A156838 := proc(n)
    add(A156837(n,k),k=1..n) ;
end proc: # R. J. Mathar, Mar 03 2013

PARI

A156348(n, k) = if(k<1 || k>n || n%k, 0, binomial(n/k-2+k, k-1)); \\ After R. J. Mathar's Maple-program in A156348
A156837(n, k) = sum(j=k,n,if(n%j, 0, A156348(j, k)));
A156838(n) = sumdiv(n,d,A156837(n,d)); \\ Antti Karttunen, Nov 30 2024

Formula

Row sums of triangle A156837.

Extensions

Extended beyond a(14) by R. J. Mathar, Mar 03 2013

More terms from Antti Karttunen, Nov 30 2024