OFFSET
1,1
COMMENTS
Suggested by reading Joshua Zucker's puzzle in Gary Antonick's Numberplay column for April 22 2013.
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..10000
Gary Antonick, The Primes in Evenland Puzzle, Numberplay Column, Wordplay Blog, New York Times, April 22, 2013
EXAMPLE
20 = 2*10 so a(5) = 2+10 = 12.
The first time there is a choice is when n=9: 36 = 2*18 = 6*6, and the latter gives the smaller sum, so a(9) = 6+6 = 12.
PROG
(PARI) f(x, i)=local(t); if(x==1, 0, if(i>#d, 2^99, t=f(x, i+1); if(x%d[i], t, min(t, d[i]+f(x/d[i], i)))))
a(n)=d=select(m->m%4==2, divisors(4*n)); f(4*n, 1) \\ Jens Kruse Andersen, Oct 01 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 30 2014
EXTENSIONS
Definition corrected and more terms from Jens Kruse Andersen, Oct 01 2014
STATUS
approved