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Search: id:A064348
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| A064348 |
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Numbers n such that n and n+1 have the same sum of unitary divisors and the same number of divisors. |
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+0
1
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| 14, 44, 1334, 1634, 2295, 2685, 3195, 17255, 33998, 42818, 45716, 79316, 84134, 122073, 124676, 125811, 166934, 239499, 289454, 294151, 383594, 440013, 544334, 605985, 649154, 655005, 736515, 1163624, 1325511, 1364104
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,75
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PROGRAM
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(PARI) {usigma(n, s=1, fac, i) = fac=factor(n); for(i=1, matsize(fac)[1], s=s*(1+fac[i, 1]^fac[i, 2]) ); return(s); } for(n=1, 10^6, if(usigma(n)==usigma(n+1) && numdiv(n)==numdiv(n+1), print1(n, ", ")))
(PARI) usigma(n)= { local(f, s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) } { n=0; s=0; d=0; for (m=1, 10^9, us=usigma(m + 1); ud=numdiv(m + 1); if(s==us && d==ud, write("b064348.txt", n++, " ", m); if (n==100, break)); s=us; d=ud ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 12 2009]
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CROSSREFS
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Cf. A034448, A000005.
Sequence in context: A089031 A033587 A009942 this_sequence A123295 A092350 A090197
Adjacent sequences: A064345 A064346 A064347 this_sequence A064349 A064350 A064351
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Oct 15 2001
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