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 A244394 Consider a number n with m decimal digits, m>1. The sequence lists the numbers n such that the prefix of length m-1 and the suffix of length m-1 both have the same sum of divisors. 1
 11, 22, 33, 44, 55, 66, 77, 88, 99, 111, 222, 333, 335, 444, 534, 551, 555, 579, 589, 666, 682, 777, 888, 954, 956, 999, 1102, 1111, 2138, 2204, 2222, 2246, 2649, 3190, 3333, 4354, 4408, 4428, 4444, 5332, 5376, 5555, 5644, 5925, 6294, 6666, 6933, 7480, 7528 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Let x(0)x(1)... x(q-1)x(q) denote the decimal expansion of a number n. The sequence lists the numbers n such that sigma(p) = sigma(s) where p is the prefix x(0)x(1)... x(q-1) and s is the suffix x(1)... x(q-1)x(q). LINKS Table of n, a(n) for n=1..49. EXAMPLE 5376 is in the sequence because sigma(537) = sigma(376) = 720. MAPLE with(numtheory): for n from 10 to 10000 do: x:=convert(n, base, 10):n1:=nops(x): s1:=sum('x[i]*10^(i-1) ', 'i'=1..n1-1): s2:=(n-irem(n, 10))/10: x1:=sigma(s1):x2:=sigma(s2): if x1 = x2 then printf(`%d, `, n): else fi: od: CROSSREFS Cf. A244282, A244283. Sequence in context: A113585 A071273 A226467 * A299792 A115853 A050785 Adjacent sequences: A244391 A244392 A244393 * A244395 A244396 A244397 KEYWORD nonn,base AUTHOR Michel Lagneau, Jun 27 2014 STATUS approved

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Last modified August 13 15:31 EDT 2024. Contains 375142 sequences. (Running on oeis4.)