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 A211225 Number of ways to represent sigma(n) as sigma(x) + sigma(y) where x+y = n. 8
 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 2, 1, 2, 0, 0, 0, 0, 1, 2, 0, 0, 0, 0, 0, 2, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,32 COMMENTS From an idea of Charles R Greathouse IV. a(A211223(n)) > 0. - Reinhard Zumkeller, Jan 06 2013 LINKS Paolo P. Lava, Table of n, a(n) for n = 1..10000 EXAMPLE a(3)=1 because sigma(3)=sigma(1)+sigma(2)=4; a(32)=2 because sigma(32)=sigma(4)+sigma(28)=sigma(14)+sigma(18)=63; a(117)=3 because sigma(117)=sigma(41)+sigma(76)=sigma(52)+sigma(65)=sigma(56)+sigma(61)=182; etc. MAPLE with(numtheory); A211225:=proc(q) local b, i, n; for n from 1 to q do   b:=0;   for i from 1 to trunc(n/2) do     if sigma(i)+sigma(n-i)=sigma(n) then b:=b+1; fi;   od;   print(b) od; end: A211225(1000); PROG (PARI) a(n)=my(t=sigma(n)); sum(i=1, n\2, sigma(i)+sigma(n-i)==t) \\ Charles R Greathouse IV, May 07 2012 (Haskell) a211225 n = length \$ filter (== a000203 n) \$ zipWith (+) us' vs where    (us, vs@(v:_)) = splitAt (fromInteger \$ (n - 1) `div` 2) a000203_list    us' = if even n then v : reverse us else reverse us -- Reinhard Zumkeller, Jan 06 2013 CROSSREFS Cf. A083207, A204830, A204831, A211223, A211224. Cf. A000203. Sequence in context: A068101 A094263 A049761 * A030618 A025448 A015010 Adjacent sequences:  A211222 A211223 A211224 * A211226 A211227 A211228 KEYWORD nonn AUTHOR Paolo P. Lava, May 07 2012 STATUS approved

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Last modified September 17 09:04 EDT 2019. Contains 327128 sequences. (Running on oeis4.)