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A034960 Divide odd numbers into groups with prime(n) elements and add together. 6
4, 21, 75, 189, 495, 897, 1683, 2565, 4071, 6641, 8959, 13209, 17835, 22317, 28623, 37577, 48439, 57401, 71623, 85697, 98623, 118737, 138195, 163493, 196231, 224321, 249775, 281945, 310759, 347249, 420751, 467801, 525943, 571985, 656047 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Hieronymus Fischer, Table of n, a(n) for n = 1..10000

FORMULA

From Hieronymus Fischer, Sep 26 2012: (Start)

a(n) = Sum_{k=(A007504(n-1)+1).. A007504(n)} (2*k-1), n > 1.

a(n) = A007504(n)^2 - A007504(n-1)^2, n > 1.

If we define A007504(0) := 0, then the formulas above are also true for n=1.

a(n) = 2*A034957(n) + A000040(n).

a(n) = 2*A034956(n) - A000040(n).

a(n) = A034959(n) + A000040(n).

(End)

EXAMPLE

{1,3} #2 S=4; {5,7,9} #3 S=21; {11,13,15,17,19} #5 S=75; {21,23,25,27,29,31,33} #7 S=189; etc.

MAPLE

S:= n-> sum(ithprime(k), k=1..n): seq(S(n+1)^2-S(n)^2, n=1..40); # Gary Detlefs, Dec 20 2011

CROSSREFS

Cf. A006003, A027441, A034959.

Cf. A007504.

Cf. A046992, A034958.

Sequence in context: A078800 A184706 A057333 * A240372 A157493 A192429

Adjacent sequences:  A034957 A034958 A034959 * A034961 A034962 A034963

KEYWORD

nonn

AUTHOR

Patrick De Geest, Oct 15 1998

STATUS

approved

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Last modified February 15 20:32 EST 2019. Contains 320138 sequences. (Running on oeis4.)