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A081421 Quotient after one division by 2 of numbers of the form 3^(2n) + 5^(2n). 0
1, 17, 353, 8177, 198593, 4912337, 122336033, 3054149297, 76315468673, 1907542343057, 47685459212513, 1192108586037617, 29802463602463553, 745059330625296977, 18626462930705797793, 465661390253305305137 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Except for the first term, these numbers always end in 3 and 7 and necessarily generate an odd number as the quotient upon a single division by 2. Indeed for even n, 3^n+5^n can be written as (4-1)^n + (4+1)^n = 4h+1 + 4i+1 for some h,i. Then we add and get 4(h+i)+2. Divide by 2 to get 2(h+i) + 1 and odd number.

LINKS

Table of n, a(n) for n=0..15.

PROG

(PARI) p3np5n(n) = { forstep(x=0, n, 2, y = (3^x + 5^x)/2; print1(y" ") ) }

CROSSREFS

Sequence in context: A324449 A191589 A194729 * A121824 A120287 A222678

Adjacent sequences:  A081418 A081419 A081420 * A081422 A081423 A081424

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Apr 20 2003

STATUS

approved

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Last modified September 18 10:31 EDT 2020. Contains 337166 sequences. (Running on oeis4.)