login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A101882 Write three numbers, skip one, write three, skip two, write three, skip three... and so on. 3
1, 2, 3, 5, 6, 7, 10, 11, 12, 16, 17, 18, 23, 24, 25, 31, 32, 33, 40, 41, 42, 50, 51, 52, 61, 62, 63, 73, 74, 75, 86, 87, 88, 100, 101, 102, 115, 116, 117, 131, 132, 133, 148, 149, 150, 166, 167, 168, 185, 186, 187, 205, 206, 207, 226, 227, 228, 248, 249, 250, 271 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Union of A052905, A052905+1, and A052905+2. - Ivan Neretin, Aug 03 2016

First terms of the 3 repeated terms belong to A052905. - 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 (1,0,2,-2,0,-1,1).

FORMULA

G.f.: x*(1+x+x^2-x^4-x^5)/ ((1+x+x^2)^2 * (1-x)^3). [Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009; checked and corrected by R. J. Mathar, Sep 16 2009]

MATHEMATICA

Flatten@Table[(n^2 + 5 n - 4)/2 + {0, 1, 2}, {n, 20}] (* Ivan Neretin, Aug 03 2016 *)

Table[Range[#, # + 2] &[(n^2 + 7 n + 2)/2], {n, 0, 20}] // Flatten (* or *)

Rest@ CoefficientList[Series[x (1 + x + x^2 - x^4 - x^5)/((1 + x + x^2)^2 (1 - x)^3), {x, 0, 61}], x] (* Michael De Vlieger, Aug 03 2016 *)

LinearRecurrence[{1, 0, 2, -2, 0, -1, 1}, {1, 2, 3, 5, 6, 7, 10}, 70] (* Harvey P. Dale, Dec 26 2019 *)

PROG

(PARI) a(n)=my(k=n%3); if(k==2, n^2+17*n-2, k==1, n^2+19*n-2, n^2+15*n)/18 \\ Charles R Greathouse IV, Aug 03 2016

CROSSREFS

Cf. A000217, A052905, A101881, A101883.

Sequence in context: A295389 A028781 A136149 * A318239 A059266 A252895

Adjacent sequences:  A101879 A101880 A101881 * A101883 A101884 A101885

KEYWORD

easy,nonn

AUTHOR

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 31 19:37 EDT 2020. Contains 333151 sequences. (Running on oeis4.)