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 A166464 a(n) = (3+2n+6n^2+4n^3)/3. 10
 1, 5, 21, 57, 121, 221, 365, 561, 817, 1141, 1541, 2025, 2601, 3277, 4061, 4961, 5985, 7141, 8437, 9881, 11481, 13245, 15181, 17297, 19601, 22101, 24805, 27721, 30857, 34221, 37821, 41665, 45761, 50117, 54741, 59641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Atomic number of first transition metal of period 2n (n>3) or of the element after n-th alkaline earth metal. This can be calculated by finding the sum of the first n even squares plus 1. - Natan Arie' Consigli, Jul 03 2016 REFERENCES JANET,Charles, La structure du Noyau de l'atome,consideree dans la Classification periodique,des elements chimiques,1927 (Novembre),N. 2,BEAUVAIS,67 pages,3 leaflets. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA a(n) = a(n-1)+4+8n+4n^2 or a(n)-a(n-1)=4*(n+1)^2 = A016742(n+1). a(n) = 2a(n-1)-a(n-2)-4+8n or a(n)-2a(n-1)+a(n-2)=-4+8n = A017113(n+1). a(n) = 3a(n-1)-3a(n-2)+a(n-3)+8 or a(n)-3a(n-1)+3a(n-2)-a(n-3)=8 =A010731. a(n) = 4a(n-1)-6a(n-2)+4a(n-3)-a(n-4) or a(n)-4a(n-1)+6a(n-2)-4a(n-3)+a(n-4)=0 = A000004(n). Binomial transform of quasi-finite sequence 1,4,12,8,0,(0 continued). G.f.: (1+x+7*x^2-x^3)/(1-x)^4. - R. J. Mathar, Feb 15 2010 a(n) = A018227(2n) + 3; a(n) = A002492(n) + 1. - Natan Arie' Consigli, Jul 03 2016 MATHEMATICA Table[(3 + 2*n + 6*n^2 + 4*n^3)/3, {n, 0, 100}](* G. C. Greubel, May 15 2016 *) PROG (PARI) a(n)=(3+2*n+6*n^2+4*n^3)/3 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Sequence in context: A146854 A299120 A033275 * A059859 A146617 A245240 Adjacent sequences:  A166461 A166462 A166463 * A166465 A166466 A166467 KEYWORD nonn,easy AUTHOR Paul Curtz, Oct 14 2009 EXTENSIONS Edited by N. J. A. Sloane, Oct 17 2009 More terms a(11)-a(35) from Vincenzo Librandi, Oct 17 2009 STATUS approved

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Last modified October 23 22:04 EDT 2018. Contains 316541 sequences. (Running on oeis4.)