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A303336 Number of rectangles with semiprime area and dimensions p,q where n = p+q and p <= q. 1
0, 0, 0, 1, 2, 1, 2, 1, 1, 3, 1, 1, 1, 2, 2, 3, 0, 2, 1, 2, 1, 4, 1, 3, 1, 4, 1, 2, 0, 3, 1, 2, 1, 5, 1, 5, 0, 2, 2, 4, 0, 4, 1, 3, 1, 4, 1, 5, 1, 5, 0, 4, 0, 5, 1, 4, 0, 5, 1, 6, 1, 3, 2, 5, 0, 7, 0, 2, 1, 6, 0, 6, 1, 5, 2, 5, 0, 8, 0, 4, 1, 5, 1, 8, 1, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Table of n, a(n) for n=1..86.

Index entries for sequences related to partitions

FORMULA

a(n) = Sum_{i=1..floor(n/2)} [Omega(i*(n-i)) = 2], where [] is the Iverson bracket and Omega = A001222.

MATHEMATICA

Table[Sum[KroneckerDelta[PrimeOmega[i (n - i)], 2], {i, Floor[n/2]}], {n, 100}]

PROG

(PARI) a(n) = sum(i=1, n\2, bigomega(i*(n-i)) == 2); \\ Michel Marcus, Apr 22 2018

CROSSREFS

Cf. A001222, A303115, A303337.

Sequence in context: A117166 A078996 A084610 * A129479 A261095 A249809

Adjacent sequences:  A303333 A303334 A303335 * A303337 A303338 A303339

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Apr 21 2018

STATUS

approved

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Last modified July 20 01:17 EDT 2019. Contains 325168 sequences. (Running on oeis4.)