OFFSET
1,1
COMMENTS
Any number of the form 20...04, with a number of consecutive zeros not equal to 6*k+4 (with k = 0, 1, 2, 3,...), appears to belong to the sequence.
EXAMPLE
antisigma(24) = (24*25) / 2 - sigma(24) = 300 - 60 = 240 and 24 is a substring;
antisigma(57) = (57*58) / 2 - sigma(57) = 1653 - 80 = 1573 and 57 is a substring.
MAPLE
with(numtheory): P:=proc(q) local a, b, c, d, j, n;
for n from 1 to q do a:=n; b:=n*(n+1)/2-sigma(n); c:=ilog10(n)+1; d:=ilog10(b)+1;
for j from 1 to d-c+1 do if n=(b mod 10^c) then print(n); break; else b:=trunc(b/10);
fi; od; od; print(); end: P(10^9);
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Paolo P. Lava, Mar 12 2015
EXTENSIONS
a(28)-a(33) from Robert Israel, Dec 20 2024
STATUS
approved