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A269862 Least monotonic left inverse of A269861. 2
0, 0, 0, 1, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 7, 8, 9, 9, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 12, 13, 13, 13, 13, 14, 14, 15, 15, 16, 16, 17, 18, 19, 20, 21, 22, 22, 22, 23, 23, 23, 24, 25, 26, 26, 27, 28, 29, 30, 30, 30, 31, 31, 32, 33, 34, 34, 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 37, 37, 38, 38, 38, 39, 39, 39, 39, 40, 41 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

a(n) = number of terms of A269861 <= n.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(1) = 0, for n > 1, a(n) = (A048673(n)-n reduced mod 2) + a(n-1).

Other identities. For all n >= 1:

a(A269861(n)) = n.

MATHEMATICA

f[n_] := (Times @@ Power[If[# == 1, 1, NextPrime@ #] & /@ First@ #, Last@ #] + 1)/2 &@ Transpose@ FactorInteger@ n; s = Select[Range@ 150, Xor[EvenQ@ f@ #, EvenQ@ #] &]; Table[Count[s, k_ /; k <= n], {n, 87}] (* Michael De Vlieger, Mar 17 2016 *)

PROG

(Scheme, with memoization-macro definec)

(definec (A269862 n) (if (<= n 1) 0 (+ (modulo (- (A048673 n) n) 2) (A269862 (- n 1)))))

CROSSREFS

Cf. A048673, A269861.

Sequence in context: A229803 A029123 A025777 * A194200 A242736 A194237

Adjacent sequences:  A269859 A269860 A269861 * A269863 A269864 A269865

KEYWORD

nonn

AUTHOR

Antti Karttunen, Mar 16 2016

STATUS

approved

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Last modified January 21 22:25 EST 2021. Contains 340359 sequences. (Running on oeis4.)