(Translated by https://www.hiragana.jp/)
A139417 - OEIS
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A139417
Sum of digits of the square of the sum of the preceding numbers.
1
1, 1, 4, 9, 9, 18, 18, 9, 18, 27, 27, 27, 18, 27, 27, 18, 27, 18, 27, 18, 9, 27, 27, 27, 27, 18, 27, 9, 27, 27, 27, 9, 27, 27, 36, 27, 27, 27, 18, 27, 27, 27, 27, 27, 36, 36, 9, 27, 27, 18, 36, 36, 27, 18, 27, 18, 27, 27, 27, 27, 36, 36, 27, 18, 36, 27, 36
OFFSET
1,3
COMMENTS
As soon as a term is 9 or multiple of 9, which is true for a(4), all following ones are also multiple of 9, which never occurs in A065075.
MATHEMATICA
nxt[{t_, a_}]:=Module[{c=Total[IntegerDigits[t^2]]}, {t+c, c}]; NestList[ nxt, {1, 1}, 70][[All, 2]] (* Harvey P. Dale, Jun 15 2021 *)
PROG
(Python)
def sd(n): return sum(map(int, str(n)))
def aupton(terms):
alst, s = [1], 1
for n in range(2, terms+1): alst.append(sd(s**2)); s += alst[-1]
return alst
print(aupton(67)) # Michael S. Branicky, Jun 15 2021
CROSSREFS
Cf. A065075.
Sequence in context: A106410 A065737 A014719 * A329732 A298816 A095873
KEYWORD
base,easy,nonn
AUTHOR
Philippe Lallouet (philip.lallouet(AT)orange.fr), Apr 20 2008
EXTENSIONS
Corrected and extended by Harvey P. Dale, Jun 15 2021
STATUS
approved