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URL: https://oeis.org/A156838

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A156838
Row sums of triangle A156837.
3
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
1,2
COMMENTS
a(n) = 3 iff n is prime.
LINKS
FORMULA
Row sums of triangle A156837.
EXAMPLE
a(4) = 7 since row 4 of triangle A156837 = (3, 3, 0, 1).
MAPLE
A156838 := proc(n)
add(A156837(n, k), k=1..n) ;
end proc: # R. J. Mathar, Mar 03 2013
PROG
(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
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Extended beyond a(14) by R. J. Mathar, Mar 03 2013
More terms from Antti Karttunen, Nov 30 2024
STATUS
approved