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A304721 Numbers m with A304720(m) = 1. 4
2, 3, 5, 7, 9, 10, 11, 12, 13, 19, 21, 23, 26, 28, 30, 39, 41, 46, 50, 51, 53, 55, 57, 59, 77, 89, 93, 101, 113, 129, 149, 151, 153, 161, 165, 178, 185, 189, 201, 221, 237, 245, 246, 297, 364, 377, 489, 553, 581, 639 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: The sequence only has 112 terms as listed in the b-file.

We have verified that there is no new term below 2*10^9.

LINKS

Zhi-Wei Sun, Table of n, a(n) for n = 1..112

Zhi-Wei Sun, Mixed sums of primes and other terms, in: D. Chudnovsky and G. Chudnovsky (eds.), Additive Number Theory, Springer, New York, 2010, pp. 341-353.

Zhi-Wei Sun, Conjectures on representations involving primes, in: M. Nathanson (ed.), Combinatorial and Additive Number Theory II, Springer Proc. in Math. & Stat., Vol. 220, Springer, Cham, 2017, pp. 279-310. (See also arXiv:1211.1588 [math.NT], 2012-2017.)

EXAMPLE

a(9) = 13 since 13 - (4^1 - 1) = 2*5 is squarefree,  13 - (4^0 - 0) = 2^2*3 is not squarefree, and 13 - (4^k -k ) < 0 for any integer k > 1.

MATHEMATICA

f[n_]:=f[n]=4^n-n;

tab={}; Do[r=0; k=0; Label[bb]; If[f[k]>=m, Goto[aa]]; If[SquareFreeQ[m-f[k]], r=r+1]; If[r>1, Goto[cc]]; k=k+1; Goto[bb]; Label[aa]; If[r==1, tab=Append[tab, m]]; Label[cc], {m, 1, 640}]; Print[tab]

CROSSREFS

Cf. A000302, A005117, A024037, A304034, A304081, A304331, A304333, A304522, A304523, A304689, A304720.

Sequence in context: A080587 A342190 A175415 * A063464 A341518 A325600

Adjacent sequences:  A304718 A304719 A304720 * A304722 A304723 A304724

KEYWORD

nonn

AUTHOR

Zhi-Wei Sun, May 17 2018

STATUS

approved

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Last modified January 17 10:21 EST 2022. Contains 350387 sequences. (Running on oeis4.)