Java Number Sum sumNforOddIndices(long n)

Description

sum Nfor Odd Indices

License

Apache License

Declaration

public static long sumNforOddIndices(long n) 

Method Source Code

//package com.java2s;
/**/* ww w. j a  va2  s . co  m*/
 *
 * maer - Solutions to problems of Project Euler
 * Copyright (C) 2011, Sandeep Gupta
 * http://www.sangupta.com/projects/maer
 *
 * The file is licensed under the the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

public class Main {
    private static double psi = (1 + Math.sqrt(5)) / 2;

    public static long sumNforOddIndices(long n) {
        // divide n by 2
        n = (n - 1) / 2;

        return getFibonnaci(2 * n + 2);
    }

    public static long getFibonnaci(long i) {
        return (long) ((Math.pow(psi, i) - Math.pow((1 - psi), i)) / Math.sqrt(5));
    }
}

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