OFFSET
1,2
COMMENTS
a(n)= (Pochhammer(5/10,n)*10^n)/5.
LINKS
FORMULA
5*a(n) = (10*n-5)(!^10) = Product_{j=1..n} (10*j-5).
E.g.f.: (-1 + (1-10*x)^(-1/2))/5.
a(n) = (Pochhammer(5/10,n)*10^n)/5.
Sum_{n>=1} 1/a(n) = exp(1/10)*sqrt(5*Pi/2)*erf(1/sqrt(10)), where erf is the error function. - Amiram Eldar, Dec 22 2022
MAPLE
seq( mul(10*j-5, j=1..n)/5, n=1..20); # G. C. Greubel, Nov 11 2019
MATHEMATICA
Table[10^n*Pochhammer[5/10, n]/5, {n, 20}] (* G. C. Greubel, Nov 11 2019 *)
PROG
(PARI) vector(20, n, prod(j=1, n, 10*j-5)/5 ) \\ G. C. Greubel, Nov 11 2019
(Magma) [(&*[10*j-5: j in [1..n]])/5: n in [1..20]]; // G. C. Greubel, Nov 11 2019
(Sage) [product( (10*j-5) for j in (1..n))/5 for n in (1..20)] # G. C. Greubel, Nov 11 2019
(GAP) List([1..20], n-> Product([1..n], j-> 10*j-5)/5 ); # G. C. Greubel, Nov 11 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved