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A309102 Nonnegative integers that are not the sum of two refactorable numbers. 0
0, 1, 5, 6, 7, 8, 12, 15, 22, 23, 28, 29, 31, 34, 35, 39, 40, 43, 46, 47, 50, 51, 53, 55, 56, 59, 63, 66, 67, 70, 71, 75, 77, 79, 83, 87, 91, 94, 95, 99, 101, 103, 107, 111, 115, 118, 119, 121, 123, 125, 127, 131, 135, 139, 142, 143, 147, 149, 151, 155, 159 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..61.

Eric Weisstein's World of Mathematics, Refactorable Number

MATHEMATICA

Flatten[Table[If[Sum[(1 - Ceiling[i/DivisorSigma[0, i]] + Floor[i/DivisorSigma[0, i]]) (1 - Ceiling[(n - i)/DivisorSigma[0, n - i]] + Floor[(n - i)/DivisorSigma[0, n - i]]), {i, Floor[n/2]}] == 0, n, {}], {n, 0, 200}]]

PROG

(PARI) isok(n) = n%numdiv(n) == 0;

is(n) = sum(j=1, n-1, isok(j)&&isok(n-j)) == 0; \\ Jinyuan Wang, Jul 27 2019

CROSSREFS

Cf. A033950, A309346.

Sequence in context: A178502 A047322 A236242 * A080703 A284682 A171405

Adjacent sequences:  A309099 A309100 A309101 * A309103 A309104 A309105

KEYWORD

nonn

AUTHOR

Wesley Ivan Hurt, Jul 27 2019

STATUS

approved

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Last modified June 28 08:51 EDT 2022. Contains 354903 sequences. (Running on oeis4.)