

A152121


a(0) = 4; for n>0, a(n) = a(n1)^2  2^(1+2^(n1))


1




OFFSET

0,1


COMMENTS

A subset of A056236, where a(n) = (2+sqrt(2))^n+(2sqrt(2))^n, when the exponent n is a nonnegative integer power of 2. I.E.: a(0) = (2+sqrt(2))^(2^0)+(2sqrt(2))^(2^0), a(1) = (2+sqrt(2))^(2^1)+(2sqrt(2))^(2^1); a(2) = (2+sqrt(2))^(2^2)+(2sqrt(2))^(2^2); etc.
For all n the value 2^(n+1) can be factored from each a(n), which except for a different initial term (a(0) = 2 instead of a(0) = 1) matches the sequence A001601 for n>0.


LINKS



FORMULA

a(n) = a(n1)^2  2^(1+2^(n1))


EXAMPLE

a(0) = 4; a(1) = 4^2  2^2 = 12; a(2) = 12^2  2^3 = 136; a(3) = 136^2  2^5 = 18464; a(4) = 18464^2  2^9 = 340918784.


CROSSREFS



KEYWORD

easy,nonn


AUTHOR

Dennis Martin (dennis.martin(AT)dptechnology.com), Nov 24 2008


STATUS

approved



