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A263086 Partial sums of A099777, where A099777(n) gives the number of divisors of n-th even number. 5
2, 5, 9, 13, 17, 23, 27, 32, 38, 44, 48, 56, 60, 66, 74, 80, 84, 93, 97, 105, 113, 119, 123, 133, 139, 145, 153, 161, 165, 177, 181, 188, 196, 202, 210, 222, 226, 232, 240, 250, 254, 266, 270, 278, 290, 296, 300, 312, 318, 327, 335, 343, 347, 359, 367, 377, 385, 391, 395, 411, 415, 421, 433, 441, 449, 461, 465, 473, 481 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10082

A. Karttunen, Ratio a(n)/A263085(n) drawn with OEIS Plot2-script

FORMULA

a(1) = 2; for n > 1, a(n) = A000005(2*n) + a(n-1). [Where A000005(k) gives the number of divisors of k.]

Other identities. For all n >= 1:

a(n) = A263084(n) + A263085(n).

MATHEMATICA

Accumulate[DivisorSigma[0, 2 Range@ 69]] (* Michael De Vlieger, Oct 13 2015 *)

PROG

(Scheme, with memoization-macro definec)

(definec (A263086 n) (if (= 1 n) (A099777 n) (+ (A099777 n) (A263086 (- n 1)))))

CROSSREFS

Cf. A000005, A006218, A099777, A263084, A263085.

Cf. also A262518, A262519.

Sequence in context: A063203 A130244 A161569 * A182814 A055025 A178805

Adjacent sequences:  A263083 A263084 A263085 * A263087 A263088 A263089

KEYWORD

nonn

AUTHOR

Antti Karttunen, Oct 12 2015

STATUS

approved

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Last modified February 24 05:37 EST 2018. Contains 299597 sequences. (Running on oeis4.)