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 A266890 Squares whose arithmetic derivative is a square. 2
 0, 1, 4, 256, 11664, 262144, 531441, 11943936, 156250000, 544195584, 4294967296, 7119140625, 24794911296, 160000000000, 195689447424, 1129718145924, 7290000000000, 8916100448256, 10851569165584, 95367431640625, 332150625000000, 406239826673664, 494424620106921 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This sequence is infinite since it contains all the numbers of the form 4^(k^2). - Giovanni Resta, May 28 2016 LINKS Table of n, a(n) for n=1..23. EXAMPLE 0' = 0 = 0^2; 1' = 0 = 0^2; 4' = 4 = 2^2; 256' = 1024 = 32^2; 11664' = 46656 = 216^2. MAPLE with(numtheory): P:=proc(q) local a, n, p; for n from 0 to q do a:=n^2*add(op(2, p)/op(1, p), p=ifactors(n^2)[2]); if trunc(sqrt(a))*trunc(sqrt(a))=a then print(n^2); fi; od; end: P(10^9); MATHEMATICA {0, 1}~Join~Select[Range[2, 10^5]^2, IntegerQ@ Sqrt[# Total[#2/#1 & @@@ FactorInteger[#]]] &] (* Michael De Vlieger, Oct 19 2021 *) PROG (PARI) ad(n) = if (n<1, 0, my(f = factor(n)); n*sum(k=1, #f~, f[k, 2]/f[k, 1])); lista(nn) = {for (n=0, nn, if (issquare(ad(n^2)), print1(n^2, ", ")); ); } \\ Michel Marcus, Apr 08 2016 CROSSREFS Cf. A000290, A003415, A008848. Sequence in context: A063073 A093760 A062075 * A013734 A209588 A085534 Adjacent sequences: A266887 A266888 A266889 * A266891 A266892 A266893 KEYWORD nonn AUTHOR Paolo P. Lava, Apr 08 2016 EXTENSIONS a(17)-a(23) from Giovanni Resta, May 28 2016 STATUS approved

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Last modified March 2 05:08 EST 2024. Contains 370460 sequences. (Running on oeis4.)