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 A163122 Composite numbers for which the sum of proper divisors equals the sum of the digit-reversed proper divisors 0
 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 21, 22, 25, 27, 33, 35, 44, 49, 55, 66, 77, 88, 99, 121, 202, 242, 262, 302, 303, 362, 363, 382, 393, 403, 404, 453, 484, 505, 524, 543, 573, 605, 606, 626, 655, 689, 706, 707, 726, 746, 755, 766, 783, 786, 808, 840, 847, 905 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA {n : n in A002808, and A001065(n) = A069250(n)}. - R. J. Mathar, Jul 27 2009 EXAMPLE 840 is in the list. The sum of its proper divisors is 1+2+3+4+5+6+7+8+10+12+14+15+20+...+280+420= A001065(840) = 2040, and the sum of the reversed proper divisors is 1+2+3+4+5+6+7+8+1+21+41+51+2+...+82+24= A069250(840) = 2040. MAPLE read("transforms") ; A001065 := proc(n) numtheory[sigma](n)-n ; end: A069250 := proc(n) local pdvs , a, d ; pdvs := numtheory[divisors](n) minus {n} ; a := 0 ; for d in pdvs do a := a+digrev(d) ; od: a ; end: for n from 4 to 1000 do if not isprime(n) and A001065(n) = A069250(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Jul 27 2009 CROSSREFS Sequence in context: A070807 A046352 A046355 * A202259 A050655 A117098 Adjacent sequences:  A163119 A163120 A163121 * A163123 A163124 A163125 KEYWORD nonn,base AUTHOR Claudio Meller, Jul 21 2009 EXTENSIONS Keyword:base added by R. J. Mathar, Jul 27 2009 STATUS approved

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