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 A108548 Fully multiplicative with a(prime(j)) = A108546(j), where A108546 is the lexicographically earliest permutation of primes such that after 2 the forms 4*k+1 and 4*k+3 alternate, and prime(j) is the j-th prime in A000040. 14
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 12, 11, 14, 15, 16, 17, 18, 19, 20, 21, 26, 29, 24, 25, 22, 27, 28, 23, 30, 37, 32, 39, 34, 35, 36, 31, 38, 33, 40, 41, 42, 43, 52, 45, 58, 53, 48, 49, 50, 51, 44, 47, 54, 65, 56, 57, 46, 61, 60, 59, 74, 63, 64, 55, 78, 73, 68, 87, 70, 67, 72 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Multiplicative with a(2^e) = 2^e, else if p is the m-th prime then a(p^e) = q^e where q is the m/2-th prime of the form 4*k + 3 (A002145) for even m and a(p^e) = r^e where r is the (m-1)/2-th prime of the form 4*k + 1 (A002144) for odd m. - David A. Corneth, Apr 25 2022 Permutation of the natural numbers with fixed points A108549: a(A108549(n)) = A108549(n). LINKS Antti Karttunen, Table of n, a(n) for n = 1..26927 MATHEMATICA terms = 72; A111745 = Module[{prs = Prime[Range[2 terms]], m3, m1, min},      m3 = Select[prs, Mod[#, 4] == 3&];      m1 = Select[prs, Mod[#, 4] == 1&];      min = Min[Length[m1], Length[m3]];      Riffle[Take[m3, min], Take[m1, min]]]; A108546[n_] := If[n == 1, 2, A111745[[n - 1]]]; A049084[n_] := PrimePi[n]*Boole[PrimeQ[n]]; a[n_] := If[n == 1, 1, Module[{p, e}, Product[{p, e} = pe; A108546[A049084[p]]^e, {pe, FactorInteger[n]}]]]; Array[a, terms] (* Jean-François Alcover, Nov 19 2021, using Harvey P. Dale's code for A111745 *) PROG (PARI) up_to = 26927; \\ One of the prime fixed points. A108546list(up_to) = { my(v=vector(up_to), p, q); v = 2; v = 3; v = 5; for(n=4, up_to, p = v[n-2]; q = nextprime(1+p); while(q%4 != p%4, q=nextprime(1+q)); v[n] = q); (v); }; v108546 = A108546list(up_to); A108546(n) = v108546[n]; A108548(n) = { my(f=factor(n)); f[, 1] = apply(A108546, apply(primepi, f[, 1])); factorback(f); }; \\ Antti Karttunen, Apr 25 2022 CROSSREFS Cf. A002144, A002145, A049084, A108546, A108549 (fixed points), A332808 (inverse permutation). Cf. also A332815, A332817 (this permutation applied to Doudna tree and its mirror image), also A332818, A332819. Cf. also A267099, A332212 and A348746 for other similar mappings. Sequence in context: A249157 A033621 A332808 * A333692 A333693 A322464 Adjacent sequences:  A108545 A108546 A108547 * A108549 A108550 A108551 KEYWORD nonn,mult,look AUTHOR Reinhard Zumkeller, Jun 10 2005 EXTENSIONS Name edited by Antti Karttunen, Apr 25 2022 STATUS approved

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Last modified September 24 17:17 EDT 2022. Contains 356945 sequences. (Running on oeis4.)