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Search: id:A082381
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| A082381 |
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Sequence of the squared digital root of a number until 1 or 4 is reached. The initial numbers 1,2,..n are not output. |
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+0
1
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| 1, 4, 9, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 25, 29, 85, 89, 145, 42, 2, 0, 4, 36, 45, 41, 17, 50, 25, 29, 85, 89, 145, 42, 20, 4, 49, 97, 130, 10, 1, 64, 52, 29, 85, 89, 145, 42, 20, 4, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 1, 2, 4, 5, 25, 29
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Conjecture: The sequence always terminates with 1 or the 4 16 37 58 89 145 42 20 4... loop.
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REFERENCES
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C. Stanley Ogilvy, Tomorrow's Math, 1972
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PROGRAM
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(PARI) \ The squared digital root of a number digitsq2(m) = {y=0; for(x=1, m, digitsq(x) ) } digitsq(n) = { while(1, s=0; while(n > 0, d=n%10; s = s+d*d; n=floor(n/10); ); print1(s" "); if(s==1 || s==4, break); n=s; ) }
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CROSSREFS
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Sequence in context: A041597 A041030 A061104 this_sequence A155931 A077530 A115551
Adjacent sequences: A082378 A082379 A082380 this_sequence A082382 A082383 A082384
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KEYWORD
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easy,nonn,uned
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Apr 13 2003
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