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 A218346 Numbers of the form a^a + b^b, with a > b > 0. 3
 5, 28, 31, 257, 260, 283, 3126, 3129, 3152, 3381, 46657, 46660, 46683, 46912, 49781, 823544, 823547, 823570, 823799, 826668, 870199, 16777217, 16777220, 16777243, 16777472, 16780341, 16823872, 17600759, 387420490, 387420493, 387420516, 387420745, 387423614, 387467145 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Subsequence of A066846. LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(1) = 2^2 + 1^1 = 5, a(2) = 3^3 + 1^1 = 28, a(3) = 2^2 + 3^3 = 31. MAPLE N:= 10^12: # for terms <= N S:= NULL: for m from 1 do v:= m^m; if v > N then break fi; S:= S, v od: sort(convert(select(`<=`, {seq(seq(S[i]+S[j], j=i+1..m-1), i=1..m-1)}, N), list)); # Robert Israel, Aug 10 2020 MATHEMATICA nn = 10; Select[Union[Flatten[Table[a^a + b^b, {a, nn}, {b, a + 1, nn}]]], # <= nn^nn + 1 &] (* T. D. Noe, Nov 15 2012 *) PROG (Python) from itertools import count, takewhile def aupto(lim):   pows = list(takewhile(lambda x: x < lim, (i**i for i in count(1))))   sums = (aa+bb for i, bb in enumerate(pows) for aa in pows[i+1:])   return sorted(set(s for s in sums if s <= lim)) print(aupto(387467145))  # Michael S. Branicky, May 28 2021 CROSSREFS Cf. A000312, A066846, A218347. Cf. A068145: primes of the form a^a + b^b. Sequence in context: A321236 A344579 A345263 * A106679 A341061 A161165 Adjacent sequences:  A218343 A218344 A218345 * A218347 A218348 A218349 KEYWORD nonn AUTHOR Alex Ratushnyak, Oct 26 2012 STATUS approved

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Last modified June 19 09:48 EDT 2021. Contains 345126 sequences. (Running on oeis4.)