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A050220 Larger of Smith brothers. 3
729, 2965, 3865, 4960, 5936, 6188, 9387, 9634, 11696, 13765, 16537, 16592, 20785, 25429, 28809, 29624, 32697, 33633, 35806, 39586, 43737, 44734, 49028, 55345, 56337, 57664, 58306, 62635, 65913, 65975, 66651, 67068, 67729, 69280, 69836 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Smith Brothers.

MAPLE

issmith:= proc(n)

  if isprime(n) then return false fi;

  convert(convert(n, base, 10), `+`) = add(t[2]*convert(convert(t[1], base, 10), `+`), t=ifactors(n)[2])

end proc:

S:= select(issmith, {$4..10^5}):

sort(convert(S intersect map(`+`, S, 1), list)); # Robert Israel, Jan 15 2018

PROG

(PARI) isone(n) = {if (!isprime(n), f = factor(n); sumdigits(n) == sum(k=1, #f~, f[k, 2]*sumdigits(f[k, 1])); ); }

isok(n) =  isone(n) && isone(n-1); \\ Michel Marcus, Jul 17 2015

CROSSREFS

Cf. A006753, A050219.

Sequence in context: A139308 A295024 A167728 * A236334 A232286 A219133

Adjacent sequences:  A050217 A050218 A050219 * A050221 A050222 A050223

KEYWORD

nonn

AUTHOR

Eric W. Weisstein

EXTENSIONS

Offset corrected by Arkadiusz Wesolowski, May 08 2012

STATUS

approved

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Last modified January 18 10:53 EST 2019. Contains 319271 sequences. (Running on oeis4.)