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Search: id:A117460
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| A117460 |
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SOD's of prime index and associated prime are both prime and SOD(i) < SOD(p) and SOD(p) is nextprime to SOD(i). This sequence consists of the primes prior to calculation of SOD. |
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3
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| 2, 3, 5, 43, 113, 191, 373, 821, 1097, 1307, 1493, 1523, 1619, 1873, 1907, 2029, 2081, 2339, 3109, 3169, 3347, 3923, 4339, 4421, 4463, 4603, 5417, 5581, 6067, 6263, 6427, 6607, 6791, 6841, 6863, 7127, 7307, 7673, 7723, 7877, 8731, 9341, 10079, 10723
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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"SOD" = "sum of digits".
Line 160 of the UBASIC program can be altered for <, >, or = relationships
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FORMULA
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Calculate SOD of both prime index and its associated prime. If SOD(i)< SOD(p) and SOD(p)is nextprime to SOD(i) then add to sequence.
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EXAMPLE
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a(5) = 113, the prime whose index is 30. SOD(30) = 3 and SOD(113) = 5. Since 3 < 5 and 5 is nextprime to 3, adjoin to sequence.
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PROGRAM
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10 'use of str, mid, len, val 20 'in SOD prime index and SOD prime 30 Y=1 40 Y=nxtprm(Y) 50 C=C+1:print C; Y; "-"; 60 D=str(C):Z=str(Y) 70 E=len(D):F=len(Z) 80 for Q=2 to E 90 A=mid(D, Q, 1):G=val(A) 100 I=I+G:print I; 110 next Q 120 for R=2 to F 130 B=mid(Z, R, 1):H=val(B) 140 J=J+H:print J; 150 next R 160 if I=prmdiv(I) and J=prmdiv(J) and I>J and I=nxtprm(J) then stop 170 I=0:J=0 180 goto 40
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CROSSREFS
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Cf. A117461, A117458-A117459, A033548-A033549.
Sequence in context: A106820 A042469 A107990 this_sequence A136371 A060380 A062608
Adjacent sequences: A117457 A117458 A117459 this_sequence A117461 A117462 A117463
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KEYWORD
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easy,nonn,base,uned
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), Mar 18 2006
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