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A145032
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If t(n) is the maximal triangular number not exceeding n, then a(n) is the n-th prime for which a(n)-t(a(n)) is a triangular number
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1
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2, 3, 7, 11, 13, 29, 31, 37, 61, 67, 79, 97, 101, 137, 139, 151, 163, 181, 191, 193, 211, 241, 263, 277, 331, 379, 409, 421, 463, 499, 571, 601, 631, 709, 739, 751, 769, 821, 823, 947, 967, 991, 1063, 1087, 1091, 1109, 1117, 1129, 1231, 1303, 1327, 1381, 1399
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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E. g., t(181)=171 (see A000217) and 181-171=10 is triangular number. Therefore p=181 is in the sequence
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MAPLE
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A057944 := proc(n) for i from 0 do if i*(i+1)/2 > n then return (i-1)*i /2 ; end if; end do: end proc:
isA000217 := proc(n) issqr(8*n+1) ; end proc:
isA145032 := proc(p) if isprime(p) then tres := p-A057944(p) ; isA000217(tres) ; else false; end if; end proc:
for n from 1 to 400 do p := ithprime(n) ; if isA145032(p) then printf("%d, ", p) ; end if; end do: (End)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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