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A284646 Variation on Leyland numbers: k = x'^y + y'^x, where x' and y' are the arithmetic derivative of x and y. 0
2, 17, 26, 37, 50, 65, 82, 101, 126, 145, 170, 197, 217, 226, 257, 325, 344, 362, 401, 442, 485, 512, 513, 577, 626, 677, 730, 785, 901, 962, 1001, 1025, 1090, 1157, 1297, 1445, 1522, 1601, 1682, 1729, 1765, 1850, 1937, 2026, 2117, 2198, 2305, 2402, 2501, 2602 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Another similar variation on Leyland numbers is k = x^y' + y^x' that leads to A014091.

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

2' = 1, 4' = 4, 1^4 + 4^2 = 1 + 16 = 17.

MAPLE

with(numtheory): N:= 10^5: A:={}: for x from 2 to floor(N^(1/2)) do

for y from 2 do yd:=y*add(op(2, p)/op(1, p), p=ifactors(y)[2]); xd:=x*add(op(2, p)/op(1, p), p=ifactors(x)[2]); a:= xd^y + yd^x;

if a>N then break fi; A:=A union {a}; od; od; sort([op(A)]);

# based on Robert Israel code in A076980.

CROSSREFS

Cf. A014091, A076980.

Sequence in context: A107137 A086322 A164275 * A270344 A171605 A018759

Adjacent sequences:  A284643 A284644 A284645 * A284647 A284648 A284649

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Mar 31 2017

STATUS

approved

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Last modified February 19 18:31 EST 2018. Contains 299356 sequences. (Running on oeis4.)