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A087279 Nonnegative numbers such that distance to nearest positive square equals exactly 1. +0
2
0, 2, 3, 5, 8, 10, 15, 17, 24, 26, 35, 37, 48, 50, 63, 65, 80, 82, 99, 101, 120, 122, 143, 145, 168, 170, 195, 197, 224, 226, 255, 257, 288, 290, 323, 325, 360, 362, 399, 401, 440, 442, 483, 485, 528, 530, 575, 577, 624, 626, 675, 677, 728, 730, 783, 785, 840 (list; graph; listen)
OFFSET

1,2

COMMENT

Union of A005563 and A002522\{1}: a(2*k+1) = (k+1)^2 - 1 = A005563(k+1); a(2*k) = k^2 + 1 = A002522(k+1); positive square + 1 or positive square - 1.

FORMULA

a(1) = 0; a(2*k+1) = a(2*k) + 2*k+1; a(2*k) = a(2*k-1) + 2.

a(n-1) = (floor(n/2) + 1)^2 - (-1)^(n mod 2).

CROSSREFS

Cf. A000290, A004526, A000035, A087278.

Sequence in context: A004977 A094568 A022955 this_sequence A084907 A158724 A036961

Adjacent sequences: A087276 A087277 A087278 this_sequence A087280 A087281 A087282

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 28 2003

EXTENSIONS

Franklin T. Adams-Watters pointed out on Jun 26 2007 that there were problems with the first couple of terems. I have made some changes, so now the definition matches the sequence. But some of the comments may need further minor adjustments. - N. J. A. Sloane (njas(AT)research.att.com), Jun 01 2008

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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