A321145 Exponential pseudoperfect numbers (A318100) equal to the sum of a subset of their proper exponential divisors in a single way.

36, 180, 252, 396, 468, 612, 684, 828, 1044, 1116, 1260, 1332, 1476, 1548, 1692, 1800, 1908, 1980, 2124, 2196, 2340, 2412, 2556, 2628, 2700, 2772, 2844, 2988, 3060, 3204, 3276, 3420, 3492, 3636, 3708, 3852, 3924, 4068, 4140, 4284, 4500, 4572, 4716, 4788, 4932

Offset

1,1

Comments

The exponential version of A064771.

Links

Table of n, a(n) for n=1..45.

Eric Weisstein's World of Mathematics, e-Divisor

Eric Weisstein's World of Mathematics, e-Perfect Number

Example

4500 is in the sequence since its proper exponential divisors are 30, 60, 90, 180, 750, 1500, 2250 and {750, 1500, 2250} is the only subset that sums to 4500.

Mathematica

dQ[n_, m_] := (n>0&&m>0 &&Divisible[n, m]); expDivQ[n_, d_] := Module[ {ft=FactorInteger[n]}, And@@MapThread[dQ, {ft[[;; , 2]], IntegerExponent[ d, ft[[;; , 1]]]} ]]; eDivs[n_] := Module[ {d=Rest[Divisors[n]]}, Select[ d, expDivQ[n, #]&] ]; esigma[1]=1; esigma[n_] := Total@eDivs[n]; eDeficientQ[n_] := esigma[n] < 2n; a = {}; n = 0; While[Length[a] < 30, n++; If[eDeficientQ[n], Continue[]]; d = Most[eDivs[n]]; c = SeriesCoefficient[Series[Product[1 + x^d[[i]], {i, Length[d]}], {x, 0, n}], n]; If[c == 1, AppendTo[a, n]]]; a

Crossrefs

Cf. A064771, A295829, A295830, A318100.

Sequence in context: A127657 A318100 A335218 * A054979 A335219 A102949

Adjacent sequences: A321142 A321143 A321144 * A321146 A321147 A321148

Keyword

nonn

Author

Amiram Eldar, Oct 28 2018

Status

approved