A193572 - OEIS

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A193572

Unhappy numbers which enter the cycle (4, 16, 37, 58, 89, 145, 42, 20) at 20.

20, 24, 204, 224, 240, 242, 402, 420, 422, 1133, 1313, 1331, 2004, 2024, 2040, 2042, 2204, 2240, 2400, 2402, 2420, 3113, 3131, 3311, 4002, 4020, 4022, 4200, 4202, 4220, 4899, 4989, 4998, 5779, 5797, 5977, 7579, 7597, 7759, 7795, 7957, 7975, 8499, 8949, 8994

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..45.

Eric Weisstein's World of Mathematics, Unhappy Number.

EXAMPLE

4899 is such a number of height 3 because it enters the cycle at 20 in 3 steps: 4899 -> 242 -> 24 -> 20 -> 4 -> 16 -> 37 -> 58 -> 89 -> 145 -> 42 -> 20 -> ...

MAPLE

S:=proc(n) local Q, k, N, z; Q:=[n]; for k from 1 do N:=convert(Q[k], base, 10); z:=sum(N['i']^2, 'i'=1..nops(N)); if not member(z, Q) then Q:=[op(Q), z]; else Q:=[op(Q), z]; break; fi; od; return Q; end:

a:=[]: for i from 1 while nops(a)<30 do Q:=S(i); A:=Q[nops(Q)]; if A=20 then a:=[op(a), i] fi; od: print(op(a));

CROSSREFS

Cf. A031177, A039943.

Sequence in context: A263016 A107302 A219392 * A167323 A112819 A070684

Adjacent sequences: A193569 A193570 A193571 * A193573 A193574 A193575

KEYWORD

nonn,base

AUTHOR

Martin Renner, Jul 31 2011

STATUS

approved