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A236856
Partial sums of A003418 starting summing from A003418(1), with a(0) = 0.
5
0, 1, 3, 9, 21, 81, 141, 561, 1401, 3921, 6441, 34161, 61881, 422241, 782601, 1142961, 1863681, 14115921, 26368161, 259160721, 491953281, 724745841, 957538401, 6311767281, 11665996161, 38437140561, 65208284961, 145521718161, 225835151361, 2554924714161
OFFSET
0,3
COMMENTS
Similar comments about the trailing digits apply here as in A173185.
a(n) gives the position of the last element of row n in irregular tables like A238280.
From a(2)=3 onward all terms are divisible by three.
a(n) is divisible by 73 for n >= 72. Therefore a(n)/3 is prime for only 13 values of n: 3, 4, 6, 8, 9, 12, 16, 22, 23, 31, 35, 48 and 53. - Amiram Eldar, Sep 19 2022
LINKS
FORMULA
a(n) = A173185(n)-1.
MATHEMATICA
Prepend[Accumulate @ Table[LCM @@ Range[n], {n, 1, 30}], 0] (* Amiram Eldar, Sep 19 2022 *)
PROG
(Scheme) (define (A236856 n) (if (< n 2) n (+ (A236856 (- n 1)) (A003418 n))))
CROSSREFS
One less than A173185.
Sequence in context: A073947 A062811 A363693 * A338534 A318843 A001470
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 27 2014
STATUS
approved