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A316946 A triple of positive integers (n,p,k) is admissible if there exist at least two different multisets of k positive integers, {x_1,x_2,...,x_k} and {y_1,y_2,...,y_k}, such that x_1+x_2+...+x_k = y_1+y_2+...+y_k = n and x_1x_2...x_k = y_1y_2...y_k = p. For each n, let A(n) = {p:(n,p,k) is admissible for some k}, and let a(n) = |A(n)|. 3
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 5, 6, 10, 14, 19, 26, 33, 43, 54, 68, 87, 106, 129, 157, 187, 226, 269, 319, 378, 445, 521, 610, 712, 825, 952, 1099, 1261, 1443, 1655, 1889, 2148, 2440, 2769, 3135, 3542, 4000, 4494, 5049, 5661, 6346, 7099, 7938, 8857, 9862, 10972, 12190, 13532, 15000, 16611, 18366 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,13

COMMENTS

John Conway proposed an interesting math puzzle in the 1960s, which is now generally known as the "Conway's wizard problem." Here is the problem.

Last night I sat behind two wizards on a bus and overheard the following:

Blue Wizard: I have a positive integer number of children, whose ages are positive integers. The sum of their ages is the number of this bus, while the product is my own age.

Red Wizard: How interesting! Perhaps if you told me your age and the number of your children, I could work out their individual ages?

Blue Wizard: No, you could not.

Red Wizard: Aha! At last, I know how old you are!

Apparently the Red Wizard had been trying to determine the Blue Wizard's age for some time. Now, what was the number of the bus?

This problem posed by Conway looks at different multisets that correspond to the same ordered triple, which motivated the study of this sequence.

LINKS

Table of n, a(n) for n=1..63.

Jay Bennett, Riddle of the week #34: Two wizards ride a bus, Popular Mechanics. Hearst Communications, Inc., 4 Aug. 2017. 12 Jun. 2018 Accessed.

John B. Kelly, Partitions with equal products, Proc. Amer. Math. Soc. 15 (1964), 987-990.

EXAMPLE

a(15) = 6 since A(15) = {36,40,48,72,96,144}:

p = 36 [9, 2, 2, 1, 1], [6, 6, 1, 1, 1]

p = 40 [10, 2, 2, 1], [8, 5, 1, 1]

p = 48 [6, 2, 2, 2, 1, 1, 1], [4, 4, 3, 1, 1, 1, 1]

p = 72 [9, 2, 2, 2], [8, 3, 3, 1], [6, 6, 2, 1],

p = 96 [8, 3, 2, 2], [6, 4, 4, 1], [6, 2, 2, 2, 2, 1], [4, 4, 3, 2, 1, 1]

p = 144 [6, 3, 2, 2, 2], [4, 4, 3, 3, 1].

MATHEMATICA

Do[repeats = {};  Do[intpart = IntegerPartitions[sum, {n}];   prod = Tally[Table[Times @@ intpart[[i]], {i, Length[intpart]}]];   repeatprod = Select[prod, #[[2]] > 1 &];   If[repeatprod != {},    repeats = Join[repeats, Transpose[repeatprod][[1]]]], {n, 3,    sum - 8}]; output = DeleteDuplicates[repeats];  Print[sum, " ", Length[output]], {sum, 12, 100}]‚Äč

CROSSREFS

Cf. A060277, A316945.

Sequence in context: A102212 A191124 A281379 * A005984 A172186 A178761

Adjacent sequences:  A316943 A316944 A316945 * A316947 A316948 A316949

KEYWORD

nonn

AUTHOR

Byungchul Cha, Adam Claman, Joshua Harrington, Ziyu Liu, Barbara Maldonado, Alexander M. Miller, Ann Palma, Wing Hong Tony Wong, Hongkwon V. Yi, Jul 20 2018

STATUS

approved

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Last modified June 16 04:56 EDT 2021. Contains 345056 sequences. (Running on oeis4.)