OFFSET
1,1
COMMENTS
Note all k>=1 are considered, even if k-2n<0. If the search space is k>=2n, variants of A020484 and A060264 appear. - R. J. Mathar, Jan 12 2013
EXAMPLE
a(15)=37 because 37 is the minimum number for which sigma(37-2*15)=sigma(7)=8 and sigma(37)-2*15=38-30=8.
MAPLE
A206770:=proc(q)
local k, n;
for n from 1 to q do
for k from 1 to q do
if sigma(k-2*n)=sigma(k)-2*n then print(k); break; fi;
od; od; end:
A206770(1000000000);
A206770 := proc(n)
local k ;
for k from 1 do
if numtheory[sigma](k-2*n) = numtheory[sigma](k)-2*n then
return k;
end if;
end do:
end proc: # R. J. Mathar, Jan 12 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Jan 10 2013
STATUS
approved