The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A171934 Backwards van Eck transform of A000010. 1
 0, 1, 0, 1, 0, 2, 0, 3, 2, 2, 0, 2, 0, 5, 0, 1, 0, 4, 0, 4, 8, 11, 0, 4, 0, 5, 8, 2, 0, 6, 0, 15, 8, 2, 0, 8, 0, 11, 4, 6, 0, 6, 0, 11, 6, 23, 0, 8, 6, 6, 0, 7, 0, 16, 14, 4, 20, 29, 0, 12, 0, 31, 6, 13, 0, 16, 0, 4, 0, 14, 0, 2, 0, 11, 20, 2, 16, 6, 0, 12, 0, 7, 0, 6, 0, 37, 0, 6, 0, 6, 18, 23, 16, 47 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS Given a sequence a, the backwards van Eck transform b is defined as follows: If a(n) has already appeared in a, let a(m) be the most recent occurrence, and set b(n)=n-m; otherwise b(n)=0. (Comment from A171899). LINKS Antti Karttunen, Table of n, a(n) for n = 1..16384 Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537 N. J. A. Sloane, Transforms MATHEMATICA Block[{a = Array[EulerPhi, 94], b = {}, m}, Do[If[! IntegerQ[m[#]], Set[m[#], i]; AppendTo[b, 0], AppendTo[b, i - m[#]]; Set[m[#], i]] &@ a[[i]], {i, Length[a]}]; b] (* Michael De Vlieger, Apr 06 2021 *) PROG (PARI) up_to = 105; backVanEck_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om, invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = i-pp, outvec[i] = 0); mapput(om, invec[i], i)); outvec; }; v171934 = backVanEck_transform(vector(up_to, n, eulerphi(n))); A171934(n) = v171934[n]; \\ Antti Karttunen, Apr 06 2021 CROSSREFS Cf. A000010. Cf. also A081373, A171899, A171900, A171932, A171933, A171936, A171941. Sequence in context: A242029 A090722 A221879 * A303205 A082785 A100949 Adjacent sequences: A171931 A171932 A171933 * A171935 A171936 A171937 KEYWORD nonn AUTHOR N. J. A. Sloane, Oct 24 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 11 06:34 EST 2023. Contains 367717 sequences. (Running on oeis4.)