OFFSET
1,1
EXAMPLE
68 * 69 / 2 - sigma(n) = 2220 and:
2 + 2 + 2 + 0 = 6;
2 + 2 + 0 + 6 = 10;
2 + 0 + 6 + 10 = 18;
0 + 6 + 10 + 18 = 34;
6 + 10 + 18 + 34 = 68.
MAPLE
with(numtheory): P:=proc(q, h) local a, b, k, n, t, v; v:=array(1..h);
for n from 2 to q do a:=n*(n+1)/2-sigma(n); b:=ilog10(a)+1; if b>1 then
for k from 1 to b do v[b-k+1]:=(a mod 10); a:=trunc(a/10); od; t:=b+1; v[t]:=add(v[k], k=1..b);
while v[t]<n do t:=t+1; v[t]:=add(v[k], k=t-b..t-1); od;
if v[t]=n then print(n); fi; fi; od; end: P(10^6, 1000);
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Paolo P. Lava, Feb 20 2017
STATUS
approved