This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A174814 a(n) = n*(n+1)*(5*n+1)/3. 2
 0, 4, 22, 64, 140, 260, 434, 672, 984, 1380, 1870, 2464, 3172, 4004, 4970, 6080, 7344, 8772, 10374, 12160, 14140, 16324, 18722, 21344, 24200, 27300, 30654, 34272, 38164, 42340, 46810, 51584, 56672, 62084, 67830, 73920, 80364, 87172, 94354, 101920, 109880 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Also zero followed by bisection (even part) of A088003. Numbers ending in 0, 2 or 4 (cf. 2*A053796(n)). Therefore we can easily see that a(m)^(2*k+1)==-1 (mod 5) only for m in A047219, while a(m)^(2*k)==-1 (mod 5) only for m in A016873 and k odd. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..2000 Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA G.f.: 2*x*(2+3*x)/(1-x)^4. a(n) = 2*A033994(n) for n>0. a(n) = n*A147875(n+1)-sum(k=1..n, A147875(k)) for n>0. a(-n) = -A144945(n). MATHEMATICA Table[1/3 n (1+n) (1+5 n), {n, 0, 50}]  (* Harvey P. Dale, Feb 25 2011 *) PROG (MAGMA) [n*(n+1)*(5*n+1)/3: n in [0..50]]; // Vincenzo Librandi, May 30 2011 (PARI) a(n) = n*(n+1)*(5*n+1)/3 \\ Charles R Greathouse IV, May 30 2011 CROSSREFS Sequence in context: A036924 A130015 A189953 * A106846 A086863 A241689 Adjacent sequences:  A174811 A174812 A174813 * A174815 A174816 A174817 KEYWORD nonn,easy AUTHOR Bruno Berselli, Dec 01 2010 - Dec 02 2010 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.

Last modified October 15 05:43 EDT 2019. Contains 328026 sequences. (Running on oeis4.)