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 A076767 Triangular numbers with square pyramidal indices. 0
 0, 1, 15, 105, 465, 1540, 4186, 9870, 20910, 40755, 74305, 128271, 211575, 335790, 515620, 769420, 1119756, 1594005, 2224995, 3051685, 4119885, 5483016, 7202910, 9350650, 12007450, 15265575, 19229301, 24015915, 29756755, 36598290 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1). FORMULA let SP(m) be the m-th square pyramidal number m*(m+1)*(2*m+1)/6 and T(k) be the k-th Triangular number k*(k+1)/2 then a(n)=T(SP(n)). G.f.: x*(1+8*x+21*x^2+10*x^3)/(1-x)^7. [Colin Barker, Apr 30 2012] EXAMPLE SP(3)=14 -> a(3)=T(SP(3))=T(14)=105; SP(4)=30 -> a(4)=T(SP(4))=T(30)=465 etc CROSSREFS Cf. A077538. Sequence in context: A202288 A010931 A282350 * A022610 A006857 A000478 Adjacent sequences: A076764 A076765 A076766 * A076768 A076769 A076770 KEYWORD easy,nonn AUTHOR Bruce Corrigan (scentman(AT)myfamily.com), Nov 14 2002 STATUS approved

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Last modified March 27 22:14 EDT 2023. Contains 361575 sequences. (Running on oeis4.)