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A112015 Numbers n with odd length such that sigma(n) = (d_1^d_2)*(d_3^d_4) *...*(d_(k-2)^d_(k-1))*d_k where d_1 d_2 ... d_k is the decimal expansion of n. 2
1, 61845, 2165527, 3045365, 4461365, 109182857, 120068526, 132268815, 154514955, 166825505, 194565915, 194621658, 215365427, 216753138, 226262568, 228330759, 243430671, 243771445, 246455605, 276514536, 276751134, 277093299, 286551243, 287337804, 293644185 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The term a(7) = 120068526 makes use of the convention 0^0 = 1. - Giovanni Resta, Jun 06 2016

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

4461365 is in the sequence because sigma(4461365)=(4^4)*(6^1)*(3^6)*5.

MATHEMATICA

Do[h=IntegerDigits[n]; k=Length[h]; If[h[[k]] != 0 && OddQ[k] && Select[Range[k/2], h[[2#-1]] == 0 ==h[[2# ]] &] == {} && DivisorSigma[1, n] == h[[k]]*Product[h[[2j-1]]^h[[2j]], {j, k/2}], Print[n]], {n, 10^7}]

CROSSREFS

Cf. A112014, A112016.

Sequence in context: A253613 A257749 A340126 * A234864 A128879 A234149

Adjacent sequences:  A112012 A112013 A112014 * A112016 A112017 A112018

KEYWORD

base,nonn

AUTHOR

Farideh Firoozbakht, Sep 14 2005

EXTENSIONS

a(6)-a(25) from Giovanni Resta, Jun 06 2016

STATUS

approved

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Last modified January 19 21:57 EST 2022. Contains 350466 sequences. (Running on oeis4.)