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 A227028 Triangular numbers whose binary conversion, read in decimal, is prime. 1
 3, 253, 595, 703, 2211, 2485, 4753, 13695, 22791, 23005, 35245, 52003, 54285, 62835, 82215, 88831, 119805, 173755, 219453, 238395, 252405, 271953, 275653, 306153, 325221, 350703, 406351, 470935, 482653, 521731, 607753, 611065, 634501, 661825, 675703, 726615 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS K. D. Bajpai and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 116 terms from Bajpai) EXAMPLE The second term a(2) = T(22) = 253. Its binary conversion is 11111101, that is a prime number when read in decimal. MAPLE with(numtheory):with(StringTools): #=Triangular numbers whose binary conversion is prime when read in decimal. PRS:= proc(x, y) local i, a, b, c, count; count:=1; for i from x to y do; a:=(1/2)*(i)*((i)+1); b:=convert(a, binary); c:=isprime(b); if c then lprint(count, a); count:=count+1; fi; od; lprint("Finished "): end: PRS(1, 5000); PROG (PARI) isA036952(n)=my(v=binary(n)); isprime(sum(i=1, #v, v[i]*10^(#v-i))) is(n)=ispolygonal(n, 3)&&isA036952(n) select(isA036952, vector(10^3, i, i*(i+1)/2)) \\ Charles R Greathouse IV, Jun 28 2013 CROSSREFS Intersection of A036952 and A000217. Sequence in context: A075901 A028918 A213409 * A279653 A320023 A045824 Adjacent sequences:  A227025 A227026 A227027 * A227029 A227030 A227031 KEYWORD nonn,base,less AUTHOR K. D. Bajpai, Jun 27 2013 STATUS approved

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Last modified June 12 16:18 EDT 2021. Contains 344959 sequences. (Running on oeis4.)