A284788 - OEIS

A284788

Even numbers that cannot be represented in at least two ways as the sum of two odd composites.

2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 32, 34, 38, 40, 44, 46, 52, 56, 62, 68

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OFFSET

1,1

COMMENTS

If n is even and n > 68, then n can be written as at least two distinct sums of two composite odd integers.

REFERENCES

D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, 1997, page 111.

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

34 is in the sequence because 34 = 9 + 25 but cannot be represented in a second way as the sum of two odd composites with 9, 15, 21, 25, 27, 33.

MATHEMATICA

oddco = Select[Range[9, 100, 2], ! PrimeQ[#] &]; Select[Range[2, 100, 2], Length@ Quiet@ IntegerPartitions[#, {2}, oddco, 2] < 2 &] (* Giovanni Resta, Apr 03 2017 *)

CROSSREFS

Cf. A118081, A284787 (complement).

Sequence in context: A084563 A194396 A321193 * A323288 A322131 A209211

Adjacent sequences: A284785 A284786 A284787 * A284789 A284790 A284791

KEYWORD

fini,full,nonn

AUTHOR

Bernard Schott, Apr 03 2017

STATUS

approved