OFFSET
0,12
COMMENTS
First 100 terms (for all two digit numbers) match with that of A069816. A088116(10a + b) = 2ab = (a+b)^2 - (a^2 + b^2) = A069816(10a + b).
The first known fixed points, after zero, are numbers of the forms 36*10^k and 1314*10^k for k >= 0. All have 9 as the sum of their digits. Calculated up to n = 10^10. - Stéphane Rézel, Jul 31 2019
LINKS
Jinyuan Wang, Table of n, a(n) for n = 0..10000
EXAMPLE
a(1234) = 234 + 2*134 + 3*124 + 4*123 = 1366.
MATHEMATICA
Join[{0}, Table[Total[IntegerDigits[n]Table[FromDigits[Drop[ IntegerDigits[ n], {d}]], {d, IntegerLength[n]}]], {n, 100}]] (* Harvey P. Dale, Dec 23 2021 *)
PROG
(PARI) a(n) = {v=digits(n); sum(k=1, #v, v[k]*(n\10^(#v-k+1)*10^(#v-k)+n%10^(#v-k))); } \\ Jinyuan Wang, Aug 01 2019
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Sep 25 2003
EXTENSIONS
More terms from David Wasserman, May 10 2005
Offset 0 from Stéphane Rézel, Jul 31 2019
STATUS
approved