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A101883 Write four numbers, skip one, write four, skip two, write four, skip three... and so on. 3
1, 2, 3, 4, 6, 7, 8, 9, 12, 13, 14, 15, 19, 20, 21, 22, 27, 28, 29, 30, 36, 37, 38, 39, 46, 47, 48, 49, 57, 58, 59, 60, 69, 70, 71, 72, 82, 83, 84, 85, 96, 97, 98, 99, 111, 112, 113, 114, 127, 128, 129, 130, 144, 145, 146, 147, 162, 163, 164, 165, 181, 182, 183, 184, 201 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Union of A051936, A051936+1, A051936+2, and A051936+3. - Ivan Neretin, Aug 03 2016

First terms of the four repeated terms belong to A051936. - Michael De Vlieger, Aug 03 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

Index entries for linear recurrences with constant coefficients, signature (1,0,0,2,-2,0,0,-1,1).

FORMULA

G.f.: x*(1+x+x^2+x^3-x^5-x^6-x^7)/ ((1+x)^2 * (x^2+1)^2 * (1-x)^3). [Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009; checked and corrected by R. J. Mathar, Sep 16 2009]

MATHEMATICA

LinearRecurrence[{1, 0, 0, 2, -2, 0, 0, -1, 1}, {1, 2, 3, 4, 6, 7, 8, 9, 12}, 80] (* or *) Rest[CoefficientList[Series[x*(1+x+x^2+x^3-x^5-x^6-x^7)/((1+x)^2(x^2+1)^2(1-x)^3), {x, 0, 80}], x]](* Harvey P. Dale, Jan 19 2016 *)

Table[Range[#, # + 3] &[n (n + 1)/2 - 9], {n, 4, 20}] // Flatten (* Michael De Vlieger, Aug 03 2016 *)

CROSSREFS

Cf. A000217, A051936, A101881, A101882.

Sequence in context: A239015 A030706 A285986 * A236207 A225837 A035246

Adjacent sequences:  A101880 A101881 A101882 * A101884 A101885 A101886

KEYWORD

easy,nonn

AUTHOR

Candace Mills (scorpiocand(AT)yahoo.com), Dec 19 2004

STATUS

approved

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Last modified August 22 11:34 EDT 2019. Contains 326176 sequences. (Running on oeis4.)