

A186129


Numbers that can be partitioned into four parts s, t, u, v such that s+k = tk = u*k = v/k for some k > 1.


1



18, 27, 32, 36, 45, 48, 50, 54, 63, 64, 72, 75, 80, 81, 90, 96, 98, 99, 100, 108, 112, 117, 125, 126, 128, 135, 144, 147, 150, 153, 160, 162, 171, 175, 176, 180, 189, 192, 196, 198, 200, 207, 208, 216, 224, 225, 234, 240, 242, 243, 245, 250, 252, 256, 261
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OFFSET

1,1


COMMENTS

Equivalently, solutions n to a*(b+1)^2 = b*n with a > b >= 2.
The general rule to obtain such a partition is to start with any number b > 1 and one of its multiples a = k*b (k > 1 and a < n) and let s = ab, t = a+b, u = a/b and v = a*b.
Sequence appears to be a subsequence of A013929, of A046790, and of A072903.


REFERENCES

JosÃ© Estalella, Ciencia Recreativa. Gustavo Gili  Editor. Barcelona, 1918, pp. 56.


LINKS

Klaus Brockhaus, Table of n, a(n) for n = 1..1178 (terms <= 5000)


EXAMPLE

18 = 2+6+2+8; for k=2 we have 2+2 = 62 = 2*2 = 8/2 = 4, hence 18 is a term.
45 = 8+12+5+20; for k=2 we have 8+2 = 122 = 5*2 = 20/2 = 10, hence 45 is a term.


PROG

(MAGMA) [ n: n in [1..300]  exists{ b: b in [2..n]  exists{ a: a in [b+1..n div 4]  n*b eq a*(b+1)^2 } } ]; // Klaus Brockhaus, Feb 15 2011


CROSSREFS

Cf. A000041, A013929, A046790, A072903.
Sequence in context: A036763 A226971 A281918 * A284672 A265738 A151741
Adjacent sequences: A186126 A186127 A186128 * A186130 A186131 A186132


KEYWORD

nonn


AUTHOR

Manuel Valdivia, Feb 13 2011


STATUS

approved



