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%I A056563 #7 Mar 31 2023 18:24:29
%S A056563 0,0,1,2,1,1,1,2,0,1,1,1,1,1,0,1,1,1,0,2,0,1,1,1,1,0,0,1,0,1,1,2,0,0,
%T A056563 1,0,1,2,0,0,1,1,1,1,0,1,0,1,0,1,0,1,1,1,1,1,0,1,0,1,0,1,0,0,1,0,1,1,
%U A056563 0,1,1,1,0,1,0,1,1,0,0,2,0,0,1,1,1,0,0,1,0,1,1,1,0,0,0,0,1,2,0,1,1,1,0,1,0
%N A056563 Number of primes which are the difference between two triangular numbers, where the larger is the n-th triangular number.
%e A056563 a(7)=2 because 7th triangular number is 28 and both 28-21=7 and 28-15=13 are primes.
%t A056563 Join[{0},Table[With[{tr=Accumulate[Range[n]]},Count[tr[[-1]]-Most[tr],_?PrimeQ]],{n,120}]] (* _Harvey P. Dale_, Mar 31 2023 *)
%Y A056563 Cf. A000217, A001227, A056562, A056564.
%K A056563 nonn
%O A056563 0,4
%A A056563 _Henry Bottomley_, Jun 27 2000
%E A056563 Formula deleted by _Harvey P. Dale_, Mar 31 2023

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