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A076980 Leyland numbers: numbers expressible as n^k + k^n nontrivially, i.e. n,k > 1 (to avoid n = (n-1)^1 +1^(n-1)). 8
8, 17, 32, 54, 57, 100, 145, 177, 320, 368, 512, 593, 945, 1124, 1649, 2169, 2530, 4240, 5392, 6250, 7073, 8361, 16580, 18785, 20412, 23401, 32993, 60049, 65792, 69632, 93312, 94932, 131361, 178478, 262468, 268705, 397585, 423393, 524649, 533169 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Crandall & Pomerance named these numbers in honor of Paul Leyland, in reference to 2638^4405 + 4405^2638, the largest known prime of this form. - Alonso del Arte, Apr 05 2006

REFERENCES

R. Crandall and C. Pomerance, Prime Numbers: A Computational Perspective, Springer, NY, 2005

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

Wikipedia, Leyland number.

EXAMPLE

a(7) = 177 because we can write 177 = 2^7 + 7^2

MATHEMATICA

Take[Sort[Flatten[Table[x^y + y^x, {x, 2, 100}, {y, x, 100}]]], 42] - Alonso del Arte, Apr 05 2006

nn=10^50; n=1; Union[Reap[While[n++; num=2*n^n; num<nn, Sow[num]; k=n; While[k++; num=n^k+k^n; num<nn, Sow[num]]]][[2, 1]]]

CROSSREFS

Prime subset of this sequence, A094133.

Sequence in context: A077221 A226601 A106648 * A209376 A159696 A049713

Adjacent sequences:  A076977 A076978 A076979 * A076981 A076982 A076983

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Oct 23 2002

EXTENSIONS

More terms from Benoit Cloitre, Oct 24 2002

More terms from Alonso del Arte, Apr 05 2006

STATUS

approved

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Last modified August 22 00:08 EDT 2014. Contains 245919 sequences.