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A007607 Skip 1, take 2, skip 3, etc.
(Formerly M0821)
5
2, 3, 7, 8, 9, 10, 16, 17, 18, 19, 20, 21, 29, 30, 31, 32, 33, 34, 35, 36, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(A000290(n)) = A001105(n). - Reinhard Zumkeller, Feb 12 2011

A057211(a(n)) = 0. - Reinhard Zumkeller, Dec 30 2011

REFERENCES

R. Honsberger, Mathematical Gems III, M.A.A., 1985, p. 177.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: 1/(1-x) * [1/(1-x) + x*sum{k>=1, (2k+1)x^(k(k+1))}]. - Ralf Stephan, Mar 03 2004

MATHEMATICA

Flatten[ Table[i, {j, 2, 16, 2}, {i, j(j - 1)/2 + 1, j(j + 1)/2}]] (* Robert G. Wilson v, Mar 11 2004 *)

PROG

(Haskell)

a007607 n = a007607_list !! (n-1)

a007607_list = skipTake 1 [1..] where

   skipTake k xs = take (k + 1) (drop k xs)

                   ++ skipTake (k + 2) (drop (2*k + 1) xs)

-- Reinhard Zumkeller, Feb 12 2011

(PARI) for(m=0, 10, for(n=2*m^2+3*m+2, 2*m^2+5*m+3, print1(n", "))) \\ Charles R Greathouse IV, Feb 12 2011

(Haskell)

a007607_list' = f $ tail $ scanl (+) 0 [1..] where

   f (t:t':t'':ts) = [t+1..t'] ++ f (t'':ts)

-- Reinhard Zumkeller, Feb 12 2011

CROSSREFS

Cf. A063656, A004202, A063657, A007606, A064801, A004202.

Complement of A007606.

Sequence in context: A284514 A268398 A249587 * A076682 A231624 A194381

Adjacent sequences:  A007604 A007605 A007606 * A007608 A007609 A007610

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Robert G. Wilson v, Mira Bernstein

STATUS

approved

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Last modified January 18 18:56 EST 2018. Contains 297864 sequences.