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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

Table of n, a(n) for n=0..29.

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 September 20 06:59 EDT 2018. Contains 315226 sequences. (Running on oeis4.)